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Spiders (
order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...
Araneae) are air-breathing
arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...
s that have eight legs, chelicerae with fangs generally able to inject
venom Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a st ...
, and spinnerets that extrude
silk Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from th ...
. They are the largest order of arachnids and rank seventh in total species diversity among all
orders Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...
of organisms. Spiders are found worldwide on every continent except for
Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...
, and have become established in nearly every land
habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
. , 50,356 spider
species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...
in 132 families have been recorded by
taxonomists In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are given ...
. However, there has been debate among scientists about how families should be classified, with over 20 different classifications proposed since 1900. Anatomically, spiders (as with all arachnids) differ from other arthropods in that the usual body segments are fused into two tagmata, the
cephalothorax The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''cepha ...
or prosoma, and the
opisthosoma The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma (cephalothorax). It is a distinctive feature of the subphylum Chelicerata (arachnids, horseshoe crabs and others). Although it is similar in most respects to ...
, or abdomen, and joined by a small, cylindrical pedicel, however, as there is currently neither paleontological nor embryological evidence that spiders ever had a separate thorax-like division, there exists an argument against the validity of the term cephalothorax, which means fused
cephalon Cephalon, Inc. was an American biopharmaceutical company co-founded in 1987 by pharmacologist Frank Baldino, Jr., neuroscientist Michael Lewis, and organic chemist James C. Kauer—all three former scientists with the DuPont Company. Baldino s ...
(head) and the
thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the c ...
. Similarly, arguments can be formed against use of the term abdomen, as the opisthosoma of all spiders contains a heart and respiratory organs, organs atypical of an abdomen. Unlike
insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...
s, spiders do not have antennae. In all except the most primitive group, the
Mesothelae The Mesothelae are a suborder of spiders (order Araneae) that includes a single extant family, Liphistiidae, and a number of extinct families. This suborder is thought to form the sister group to all other living spiders, and to retain ancestral ...
, spiders have the most centralized nervous systems of all arthropods, as all their
ganglia A ganglion is a group of neuron cell bodies in the peripheral nervous system. In the somatic nervous system this includes dorsal root ganglia and trigeminal ganglia among a few others. In the autonomic nervous system there are both sympathe ...
are fused into one mass in the cephalothorax. Unlike most arthropods, spiders have no extensor muscles in their limbs and instead extend them by hydraulic pressure. Their abdomens bear appendages that have been modified into spinnerets that extrude silk from up to six types of glands. Spider webs vary widely in size, shape and the amount of sticky thread used. It now appears that the spiral orb web may be one of the earliest forms, and spiders that produce tangled cobwebs are more abundant and diverse than orb-weaver spiders. Spider-like arachnids with silk-producing spigots appeared in the
Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wh ...
period about , but these animals apparently lacked spinnerets. True spiders have been found in
Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferou ...
rocks from , and are very similar to the most primitive surviving
suborder Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...
, the
Mesothelae The Mesothelae are a suborder of spiders (order Araneae) that includes a single extant family, Liphistiidae, and a number of extinct families. This suborder is thought to form the sister group to all other living spiders, and to retain ancestral ...
. The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appeared in the Triassic period, before . The species '' Bagheera kiplingi'' was described as herbivorous in 2008, but all other known species are
predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill t ...
s, mostly preying on insects and on other spiders, although a few large species also take birds and lizards. It is estimated that the world's 25 million tons of spiders kill 400–800 million tons of prey per year. Spiders use a wide range of strategies to capture prey: trapping it in sticky webs, lassoing it with sticky bolas, mimicking the prey to avoid detection, or running it down. Most detect prey mainly by sensing vibrations, but the active hunters have acute vision, and hunters of the
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
''
Portia Portia may refer to: Biology * ''Portia'' (spider), a genus of jumping spiders *'' Anaea troglodyta'' or Portia, a brush-footed butterfly *Portia tree, a plant native to Polynesia Medication A form of birth control made of ethinylestradiol/lev ...
'' show signs of intelligence in their choice of tactics and ability to develop new ones. Spiders' guts are too narrow to take solids, so they liquefy their food by flooding it with digestive
enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
s. They also grind food with the bases of their pedipalps, as arachnids do not have the mandibles that crustaceans and insects have. To avoid being eaten by the females, which are typically much larger, male spiders identify themselves to potential mates by a variety of complex
courtship Courtship is the period wherein some couples get to know each other prior to a possible marriage. Courtship traditionally may begin after a betrothal and may conclude with the celebration of marriage. A courtship may be an informal and private m ...
rituals. Males of most species survive a few matings, limited mainly by their short life spans. Females weave silk egg-cases, each of which may contain hundreds of eggs. Females of many species care for their young, for example by carrying them around or by sharing food with them. A minority of species are social, building communal webs that may house anywhere from a few to 50,000 individuals. Social behavior ranges from precarious toleration, as in the widow spiders, to co-operative hunting and food-sharing. Although most spiders live for at most two years,
tarantula Tarantulas comprise a group of large and often hairy spiders of the family Theraphosidae. , 1,040 species have been identified, with 156 genera. The term "tarantula" is usually used to describe members of the family Theraphosidae, although m ...
s and other mygalomorph spiders can live up to 25 years in captivity. While the venom of a few species is dangerous to humans, scientists are now researching the use of spider venom in medicine and as non-polluting
pesticide Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and ...
s. Spider silk provides a combination of lightness, strength and elasticity that is superior to that of synthetic materials, and spider silk genes have been inserted into
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...
s and
plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae excl ...
s to see if these can be used as silk factories. As a result of their wide range of behaviors, spiders have become common symbols in art and
mythology Myth is a folklore genre consisting of narratives that play a fundamental role in a society, such as foundational tales or origin myths. Since "myth" is widely used to imply that a story is not objectively true, the identification of a narra ...
symbolizing various combinations of patience, cruelty and creative powers. An irrational fear of spiders is called
arachnophobia Arachnophobia is a specific phobia brought about by the irrational fear of spiders and other arachnids such as scorpions. Signs and symptoms People with arachnophobia tend to feel uneasy in any area they believe could harbour spiders or that ...
.


Etymology

The word ''spider'' derives from
Proto-Germanic Proto-Germanic (abbreviated PGmc; also called Common Germanic) is the reconstructed proto-language of the Germanic branch of the Indo-European languages. Proto-Germanic eventually developed from pre-Proto-Germanic into three Germanic br ...
,
literally ''Literally'' is an English adverb. It has been controversially used as an intensifier for figurative statements. History The first known use of the word ''literally'' was in the 15th century, or the 1530s, when it was used in the sense of "in ...
(a reference to how spiders make their webs), from the Proto-Indo-European root .


Description


Body plan

Spiders are
chelicerate The subphylum Chelicerata (from New Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. It contains the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks, and mite ...
s and therefore
arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...
s. As arthropods they have: segmented bodies with jointed limbs, all covered in a
cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...
made of
chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...
and proteins; heads that are composed of several segments that fuse during the development of the
embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...
. Being chelicerates, their bodies consist of two tagmata, sets of segments that serve similar functions: the foremost one, called the
cephalothorax The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''cepha ...
or
prosoma The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''cepha ...
, is a complete fusion of the segments that in an
insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...
would form two separate tagmata, the
head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals ...
and
thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the c ...
; the rear tagma is called the
abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the to ...
or
opisthosoma The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma (cephalothorax). It is a distinctive feature of the subphylum Chelicerata (arachnids, horseshoe crabs and others). Although it is similar in most respects to ...
. In spiders, the cephalothorax and abdomen are connected by a small cylindrical section, the pedicel. The pattern of segment fusion that forms chelicerates' heads is unique among arthropods, and what would normally be the first head segment disappears at an early stage of development, so that chelicerates lack the antennae typical of most arthropods. In fact, chelicerates' only
appendage An appendage (or outgrowth) is an external body part, or natural prolongation, that protrudes from an organism's body. In arthropods, an appendage refers to any of the homologous body parts that may extend from a body segment, including ante ...
s ahead of the mouth are a pair of chelicerae, and they lack anything that would function directly as "jaws". The first appendages behind the mouth are called pedipalps, and serve different functions within different groups of chelicerates. Spiders and
scorpion Scorpions are predatory arachnids of the order Scorpiones. They have eight legs, and are easily recognized by a pair of grasping pincers and a narrow, segmented tail, often carried in a characteristic forward curve over the back and always en ...
s are members of one chelicerate group, the arachnids. Scorpions' chelicerae have three sections and are used in feeding. Spiders' chelicerae have two sections and terminate in
fang A fang is a long, pointed tooth. In mammals, a fang is a modified maxillary tooth, used for biting and tearing flesh. In snakes, it is a specialized tooth that is associated with a venom gland (see snake venom). Spiders also have external fa ...
s that are generally
venom Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a st ...
ous, and fold away behind the upper sections while not in use. The upper sections generally have thick "beards" that filter solid lumps out of their food, as spiders can take only liquid food. Scorpions' pedipalps generally form large claws for capturing prey, while those of spiders are fairly small appendages whose bases also act as an extension of the mouth; in addition, those of male spiders have enlarged last sections used for
sperm Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, ...
transfer. In spiders, the cephalothorax and abdomen are joined by a small, cylindrical pedicel, which enables the abdomen to move independently when producing
silk Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from th ...
. The upper surface of the cephalothorax is covered by a single,
convex Convex or convexity may refer to: Science and technology * Convex lens, in optics Mathematics * Convex set, containing the whole line segment that joins points ** Convex polygon, a polygon which encloses a convex set of points ** Convex polytop ...
carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...
, while the underside is covered by two rather flat plates. The abdomen is soft and egg-shaped. It shows no sign of segmentation, except that the primitive
Mesothelae The Mesothelae are a suborder of spiders (order Araneae) that includes a single extant family, Liphistiidae, and a number of extinct families. This suborder is thought to form the sister group to all other living spiders, and to retain ancestral ...
, whose living members are the
Liphistiidae The spider family Liphistiidae, recognized by Tamerlan Thorell in 1869, comprises 8 genera and about 100 species of medium-sized spiders from Southeast Asia, China, and Japan. They are among the most basal living spiders, belonging to the subord ...
, have segmented plates on the upper surface.


Circulation and respiration

Like other arthropods, spiders are
coelom The coelom (or celom) is the main body cavity in most animals and is positioned inside the body to surround and contain the digestive tract and other organs. In some animals, it is lined with mesothelium. In other animals, such as molluscs, ...
ates in which the coelom is reduced to small areas around the reproductive and excretory systems. Its place is largely taken by a
hemocoel The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, t ...
, a cavity that runs most of the length of the body and through which
blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...
flows. The heart is a tube in the upper part of the body, with a few ostia that act as non-return valves allowing blood to enter the heart from the hemocoel but prevent it from leaving before it reaches the front end. However, in spiders, it occupies only the upper part of the abdomen, and blood is discharged into the hemocoel by one artery that opens at the rear end of the abdomen and by branching arteries that pass through the pedicle and open into several parts of the cephalothorax. Hence spiders have open
circulatory system The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...
s. The blood of many spiders that have
book lung A book lung is a type of respiration organ used for atmospheric gas exchange that is present in many arachnids, such as scorpions and spiders. Each of these organs is located inside an open ventral abdominal, air-filled cavity (atrium) and conn ...
s contains the
respiratory pigment A respiratory pigment is a metalloprotein that serves a variety of important functions, its main being O2 transport. Other functions performed include O2 storage, CO2 transport, and transportation of substances other than respiratory gases. There ar ...
hemocyanin to make
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
transport more efficient. Spiders have developed several different respiratory anatomies, based on
book lung A book lung is a type of respiration organ used for atmospheric gas exchange that is present in many arachnids, such as scorpions and spiders. Each of these organs is located inside an open ventral abdominal, air-filled cavity (atrium) and conn ...
s, a
trachea The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air- breathing animals with lungs. The trachea extends from t ...
l system, or both. Mygalomorph and
Mesothelae The Mesothelae are a suborder of spiders (order Araneae) that includes a single extant family, Liphistiidae, and a number of extinct families. This suborder is thought to form the sister group to all other living spiders, and to retain ancestral ...
spiders have two pairs of
book lung A book lung is a type of respiration organ used for atmospheric gas exchange that is present in many arachnids, such as scorpions and spiders. Each of these organs is located inside an open ventral abdominal, air-filled cavity (atrium) and conn ...
s filled with haemolymph, where openings on the ventral surface of the abdomen allow air to enter and diffuse
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
. This is also the case for some basal araneomorph spiders, like the family Hypochilidae, but the remaining members of this group have just the anterior pair of book lungs intact while the posterior pair of breathing organs are partly or fully modified into tracheae, through which oxygen is diffused into the haemolymph or directly to the tissue and organs. The tracheal system has most likely evolved in small ancestors to help resist
desiccation Desiccation () is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. ...
. The trachea were originally connected to the surroundings through a pair of openings called spiracles, but in the majority of spiders this pair of spiracles has fused into a single one in the middle, and moved backwards close to the
spinneret A spinneret is a silk-spinning organ of a spider or the larva of an insect. Some adult insects also have spinnerets, such as those borne on the forelegs of Embioptera. Spinnerets are usually on the underside of a spider's opisthosoma, and are ...
s. Spiders that have tracheae generally have higher
metabolic rate Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
s and better water conservation. Spiders are
ectotherm An ectotherm (from the Greek () "outside" and () "heat") is an organism in which internal physiological sources of heat are of relatively small or of quite negligible importance in controlling body temperature.Davenport, John. Animal Life ...
s, so environmental temperatures affect their activity.


Feeding, digestion and excretion

Uniquely among
chelicerate The subphylum Chelicerata (from New Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. It contains the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks, and mite ...
s, the final sections of spiders' chelicerae are fangs, and the great majority of spiders can use them to inject
venom Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a st ...
into prey from venom
gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland). Structure De ...
s in the roots of the chelicerae. The families Uloboridae and Holarchaeidae, and some
Liphistiidae The spider family Liphistiidae, recognized by Tamerlan Thorell in 1869, comprises 8 genera and about 100 species of medium-sized spiders from Southeast Asia, China, and Japan. They are among the most basal living spiders, belonging to the subord ...
spiders, have lost their venom glands, and kill their prey with silk instead. Like most arachnids, including
scorpion Scorpions are predatory arachnids of the order Scorpiones. They have eight legs, and are easily recognized by a pair of grasping pincers and a narrow, segmented tail, often carried in a characteristic forward curve over the back and always en ...
s, spiders have a narrow gut that can only cope with liquid food and two sets of filters to keep solids out. They use one of two different systems of external digestion. Some pump digestive
enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
s from the midgut into the prey and then suck the liquified tissues of the prey into the gut, eventually leaving behind the empty husk of the prey. Others grind the prey to pulp using the chelicerae and the bases of the pedipalps, while flooding it with enzymes; in these species, the chelicerae and the bases of the pedipalps form a preoral cavity that holds the food they are processing. The stomach in the cephalothorax acts as a pump that sends the food deeper into the digestive system. The midgut bears many digestive ceca, compartments with no other exit, that extract nutrients from the food; most are in the abdomen, which is dominated by the digestive system, but a few are found in the cephalothorax. Most spiders convert
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
ous waste products into uric acid, which can be excreted as a dry material.
Malphigian tubules The Malpighian tubule system is a type of excretory and osmoregulatory system found in some insects, myriapods, arachnids and tardigrades. The system consists of branching tubules extending from the alimentary canal that absorbs solutes, water ...
("little tubes") extract these wastes from the blood in the hemocoel and dump them into the
cloaca In animal anatomy, a cloaca ( ), plural cloacae ( or ), is the posterior orifice that serves as the only opening for the digestive, reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles and birds, ...
l chamber, from which they are expelled through the
anus The anus (Latin, 'ring' or 'circle') is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, the residual semi-solid waste that remains after food digestion, which, ...
. Production of uric acid and its removal via Malphigian tubules are a water-conserving feature that has evolved independently in several
arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...
lineages that can live far away from water, for example the tubules of
insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...
s and arachnids develop from completely different parts of the
embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...
. However, a few primitive spiders, the sub
order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...
Mesothelae The Mesothelae are a suborder of spiders (order Araneae) that includes a single extant family, Liphistiidae, and a number of extinct families. This suborder is thought to form the sister group to all other living spiders, and to retain ancestral ...
and infraorder Mygalomorphae, retain the ancestral arthropod nephridia ("little
kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blo ...
s"), which use large amounts of water to excrete nitrogenous waste products as
ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous ...
.


Central nervous system

The basic arthropod
central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
consists of a pair of nerve cords running below the gut, with paired
ganglia A ganglion is a group of neuron cell bodies in the peripheral nervous system. In the somatic nervous system this includes dorsal root ganglia and trigeminal ganglia among a few others. In the autonomic nervous system there are both sympathe ...
as local control centers in all segments; a brain formed by fusion of the ganglia for the head segments ahead of and behind the mouth, so that the
esophagus The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to t ...
is encircled by this conglomeration of ganglia. Except for the primitive
Mesothelae The Mesothelae are a suborder of spiders (order Araneae) that includes a single extant family, Liphistiidae, and a number of extinct families. This suborder is thought to form the sister group to all other living spiders, and to retain ancestral ...
, of which the
Liphistiidae The spider family Liphistiidae, recognized by Tamerlan Thorell in 1869, comprises 8 genera and about 100 species of medium-sized spiders from Southeast Asia, China, and Japan. They are among the most basal living spiders, belonging to the subord ...
are the sole surviving family, spiders have the much more centralized nervous system that is typical of arachnids: ''all'' the ganglia of all segments behind the esophagus are fused, so that the cephalothorax is largely filled with nervous tissue and there are no ganglia in the abdomen; in the Mesothelae, the ganglia of the abdomen and the rear part of the cephalothorax remain unfused. Despite the relatively small central nervous system, some spiders (like ''
Portia Portia may refer to: Biology * ''Portia'' (spider), a genus of jumping spiders *'' Anaea troglodyta'' or Portia, a brush-footed butterfly *Portia tree, a plant native to Polynesia Medication A form of birth control made of ethinylestradiol/lev ...
'') exhibit complex behaviour, including the ability to use a trial-and-error approach.


Sense organs


Eyes

Spiders have primarily four pairs of eyes on the top-front area of the cephalothorax, arranged in patterns that vary from one family to another. The principal pair at the front are of the type called pigment-cup
ocelli A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-l ...
("little eyes"), which in most
arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...
s are only capable of detecting the direction from which light is coming, using the shadow cast by the walls of the cup. However, in spiders these eyes are capable of forming images. The other pairs, called secondary eyes, are thought to be derived from the
compound eye A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which disti ...
s of the ancestral
chelicerate The subphylum Chelicerata (from New Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. It contains the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks, and mite ...
s, but no longer have the separate facets typical of compound eyes. Unlike the principal eyes, in many spiders these secondary eyes detect light reflected from a reflective tapetum lucidum, and
wolf spider Wolf spiders are members of the family Lycosidae (). They are robust and agile hunters with excellent eyesight. They live mostly in solitude, hunt alone, and do not spin webs. Some are opportunistic hunters, pouncing upon prey as they find it or ...
s can be spotted by torchlight reflected from the tapeta. On the other hand, the secondary eyes of jumping spiders have no tapeta. Other differences between the principal and secondary eyes are that the latter have rhabdomeres that point away from incoming light, just like in vertebrates, while the arrangement is the opposite in the former. The principal eyes are also the only ones with eye muscles, allowing them to move the retina. Having no muscles, the secondary eyes are immobile. The
visual acuity Visual acuity (VA) commonly refers to the clarity of vision, but technically rates an examinee's ability to recognize small details with precision. Visual acuity is dependent on optical and neural factors, i.e. (1) the sharpness of the retinal ...
of some jumping spiders exceeds by a factor of ten that of dragonflies, which have by far the best vision among
insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...
s. This acuity is achieved by a telephotographic series of lenses, a four-layer retina, and the ability to swivel the eyes and integrate images from different stages in the scan. The downside is that the scanning and integrating processes are relatively slow. There are spiders with a reduced number of eyes, the most common having six eyes (example, '' Periegops suterii'') with a pair of eyes absent on the anterior median line. Other species have four eyes and members of the
Caponiidae Caponiidae is a family of ecribellate haplogyne spiders that are unusual in a number of ways. They differ from other spiders in lacking book lungs and having the posterior median spinnerets anteriorly displaced to form a transverse row with the a ...
family can have as few as two. Cave dwelling species have no eyes, or possess vestigial eyes incapable of sight.


Other senses

As with other arthropods, spiders'
cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...
s would block out information about the outside world, except that they are penetrated by many sensors or connections from sensors to the nervous system. In fact, spiders and other arthropods have modified their cuticles into elaborate arrays of sensors. Various touch sensors, mostly bristles called
seta In biology, setae (singular seta ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. ...
e, respond to different levels of force, from strong contact to very weak air currents. Chemical sensors provide equivalents of
taste The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste (flavor). Taste is the perception produced or stimulated when a substance in the mouth reacts chemically with taste receptor ...
and smell, often by means of setae. An adult ''
Araneus ''Araneus'' is a genus of common orb-weaving spiders. It includes about 650 species, among which are the European garden spider and the barn spider. The genus was erected by Carl Alexander Clerck in 1757. Description Spiders of this genus pr ...
'' may have up to 1,000 such chemosensitive setae, most on the tarsi of the first pair of legs. Males have more chemosensitive bristles on their pedipalps than females. They have been shown to be responsive to sex pheromones produced by females, both contact and air-borne. The jumping spider ''
Evarcha culicivora ''Evarcha culicivora'' is a species of jumping spider (family Salticidae) found only around Lake Victoria in Kenya and Uganda. At maturity, ''E. culicivora'' spiders have an average size of 5 mm for both males and females. The range in ...
'' uses the scent of blood from mammals and other vertebrates, which is obtained by capturing blood-filled
mosquito Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning " gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "li ...
es, to attract the opposite sex. Because they are able to tell the sexes apart, it is assumed the blood scent is mixed with pheromones. Spiders also have in the joints of their limbs
slit sensilla The slit sensilla, also known as the slit sense organ, is a small mechanoreceptory organ or group of organs in the exoskeleton of arachnids which detects physical deformation or strain due to forces experienced by the animal. The organ appears in ...
e that detect force and vibrations. In web-building spiders, all these mechanical and chemical sensors are more important than the eyes, while the eyes are most important to spiders that hunt actively. Like most arthropods, spiders lack balance and
acceleration In mechanics, acceleration is the rate of change of the velocity of an object with respect to time. Accelerations are vector quantities (in that they have magnitude and direction). The orientation of an object's acceleration is given by ...
sensors and rely on their eyes to tell them which way is up. Arthropods' proprioceptors, sensors that report the force exerted by muscles and the degree of bending in the body and joints, are well-understood. On the other hand, little is known about what other internal sensors spiders or other arthropods may have. Some spiders use their webs for hearing, where the giant webs function as extended and reconfigurable auditory sensors.


Locomotion

Each of the eight legs of a spider consists of seven distinct parts. The part closest to and attaching the leg to the cephalothorax is the coxa; the next segment is the short trochanter that works as a hinge for the following long segment, the
femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates ...
; next is the spider's knee, the
patella The patella, also known as the kneecap, is a flat, rounded triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. The patella is found in many tetrapods, such as ...
, which acts as the hinge for the
tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it conn ...
; the
metatarsus The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the me ...
is next, and it connects the tibia to the tarsus (which may be thought of as a foot of sorts); the tarsus ends in a claw made up of either two or three points, depending on the family to which the spider belongs. Although all arthropods use muscles attached to the inside of the exoskeleton to flex their limbs, spiders and a few other groups still use hydraulic pressure to extend them, a system inherited from their pre-arthropod ancestors. The only extensor muscles in spider legs are located in the three hip joints (bordering the coxa and the trochanter). As a result, a spider with a punctured
cephalothorax The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''cepha ...
cannot extend its legs, and the legs of dead spiders curl up. Spiders can generate pressures up to eight times their resting level to extend their legs, and jumping spiders can jump up to 50 times their own length by suddenly increasing the blood pressure in the third or fourth pair of legs. Although larger spiders use hydraulics to straighten their legs, unlike smaller jumping spiders they depend on their flexor muscles to generate the propulsive force for their jumps. Most spiders that hunt actively, rather than relying on webs, have dense tufts of fine bristles between the paired claws at the tips of their legs. These tufts, known as scopulae, consist of bristles whose ends are split into as many as 1,000 branches, and enable spiders with scopulae to walk up vertical glass and upside down on ceilings. It appears that scopulae get their grip from contact with extremely thin layers of water on surfaces. Spiders, like most other arachnids, keep at least four legs on the surface while walking or running.


Silk production

The abdomen has no appendages except those that have been modified to form one to four (usually three) pairs of short, movable
spinneret A spinneret is a silk-spinning organ of a spider or the larva of an insect. Some adult insects also have spinnerets, such as those borne on the forelegs of Embioptera. Spinnerets are usually on the underside of a spider's opisthosoma, and are ...
s, which emit
silk Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from th ...
. Each spinneret has many spigots, each of which is connected to one silk
gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland). Structure De ...
. There are at least six types of silk gland, each producing a different type of silk.
Spitting spider Spitting spiders (Scytodidae) is a family of araneomorph spiders first described by John Blackwall in 1864. It contains over 250 species in five genera, of which '' Scytodes'' is the best-known. Description Like recluse spiders and coneweb sp ...
s also produce silk in modified venom glands. Silk is mainly composed of a
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
very similar to that used in insect silk. It is initially a liquid, and hardens not by exposure to air but as a result of being drawn out, which changes the internal structure of the protein. It is similar in tensile strength to
nylon Nylon is a generic designation for a family of synthetic polymers composed of polyamides ( repeating units linked by amide links).The polyamides may be aliphatic or semi-aromatic. Nylon is a silk-like thermoplastic, generally made from pet ...
and biological materials such as
chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...
,
collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whol ...
and
cellulose Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wa ...
, but is much more
elastic Elastic is a word often used to describe or identify certain types of elastomer, elastic used in garments or stretchable fabrics. Elastic may also refer to: Alternative name * Rubber band, ring-shaped band of rubber used to hold objects togethe ...
. In other words, it can stretch much further before breaking or losing shape. Some spiders have a cribellum, a modified spinneret with up to 40,000 spigots, each of which produces a single very fine fiber. The fibers are pulled out by the calamistrum, a comblike set of bristles on the jointed tip of the cribellum, and combined into a composite woolly thread that is very effective in snagging the bristles of insects. The earliest spiders had cribella, which produced the first silk capable of capturing insects, before spiders developed silk coated with sticky droplets. However, most modern groups of spiders have lost the cribellum. Even species that do not build webs to catch prey use silk in several ways: as wrappers for
sperm Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, ...
and for fertilized eggs; as a " safety rope"; for nest-building; and as "
parachute A parachute is a device used to slow the motion of an object through an atmosphere by creating drag or, in a ram-air parachute, aerodynamic lift. A major application is to support people, for recreation or as a safety device for aviators, w ...
s" by the young of some species.


Reproduction and life cycle

Spiders reproduce sexually and fertilization is internal but indirect, in other words the
sperm Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, ...
is not inserted into the female's body by the male's genitals but by an intermediate stage. Unlike many land-living
arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...
s, male spiders do not produce ready-made
spermatophore A spermatophore or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especially salamanders and arthropods, and transferred in entirety to the female's ovipore during reproduction. Spermatophore ...
s (packages of sperm), but spin small sperm webs onto which they ejaculate and then transfer the sperm to special
syringe A syringe is a simple reciprocating pump consisting of a plunger (though in modern syringes, it is actually a piston) that fits tightly within a cylindrical tube called a barrel. The plunger can be linearly pulled and pushed along the inside ...
-styled structures, palpal bulbs or palpal organs, borne on the tips of the pedipalps of mature males. When a male detects signs of a female nearby he checks whether she is of the same species and whether she is ready to mate; for example in species that produce webs or "safety ropes", the male can identify the species and sex of these objects by "smell". Spiders generally use elaborate
courtship Courtship is the period wherein some couples get to know each other prior to a possible marriage. Courtship traditionally may begin after a betrothal and may conclude with the celebration of marriage. A courtship may be an informal and private m ...
rituals to prevent the large females from eating the small males before fertilization, except where the male is so much smaller that he is not worth eating. In web-weaving species, precise patterns of vibrations in the web are a major part of the rituals, while patterns of touches on the female's body are important in many spiders that hunt actively, and may "hypnotize" the female. Gestures and dances by the male are important for
jumping spider Jumping spiders are a group of spiders that constitute the family Salticidae. As of 2019, this family contained over 600 described genera and over 6,000 described species, making it the largest family of spiders at 13% of all species. Jumping spi ...
s, which have excellent eyesight. If courtship is successful, the male injects his sperm from the palpal bulbs into the female via one or two openings on the underside of her abdomen. Female spiders' reproductive tracts are arranged in one of two ways. The ancestral arrangement ("haplogyne" or "non-entelegyne") consists of a single genital opening, leading to two seminal receptacles (spermathecae) in which females store sperm. In the more advanced arrangement ("entelegyne"), there are two further openings leading directly to the spermathecae, creating a "flow through" system rather than a "first-in first-out" one. Eggs are as a general rule only fertilized during oviposition when the stored sperm is released from its chamber, rather than in the ovarian cavity. A few exceptions exist, such as '' Parasteatoda tepidariorum''. In these species the female appears to be able to activate the dormant sperm before oviposition, allowing them to migrate to the ovarian cavity where fertilization occurs. The only known example of direct fertilization between male and female is an Israeli spider, '' Harpactea sadistica'', which has evolved traumatic insemination. In this species the male will penetrate its pedipalps through the female's body wall and inject his sperm directly into her ovaries, where the embryos inside the fertilized eggs will start to develop before being laid. Males of the
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
'' Tidarren'' amputate one of their palps before maturation and enter adult life with one palp only. The palps are 20% of the male's body mass in this species, and detaching one of the two improves mobility. In the
Yemen Yemen (; ar, ٱلْيَمَن, al-Yaman), officially the Republic of Yemen,, ) is a country in Western Asia. It is situated on the southern end of the Arabian Peninsula, and borders Saudi Arabia to the north and Oman to the northeast and ...
i species ''Tidarren argo'', the remaining palp is then torn off by the female. The separated palp remains attached to the female's epigynum for about four hours and apparently continues to function independently. In the meantime, the female feeds on the palpless male. In over 60% of cases, the female of the Australian redback spider kills and eats the male after it inserts its second palp into the female's genital opening; in fact, the males co-operate by trying to impale themselves on the females' fangs. Observation shows that most male redbacks never get an opportunity to mate, and the "lucky" ones increase the likely number of offspring by ensuring that the females are well-fed. However, males of most species survive a few matings, limited mainly by their short life spans. Some even live for a while in their mates' webs. DirkvdM Nephila clavipes.jpg, The tiny male of the golden orb weaver (''
Trichonephila clavipes ''Trichonephila clavipes'' (formerly known as ''Nephila clavipes''), commonly known as the golden silk orb-weaver, golden silk spider, or banana spider (a name shared with several others), is an orb-weaving spider species which inhabits forests ...
'') (near the top of the leaf) is protected from the female by producing the right vibrations in the web, and may be too small to be worth eating. Orange spider egg sac.jpg, Orange spider egg sac hanging from ceiling Gasteracantha mammosa spiderlings next to their eggs capsule.jpg, ''
Gasteracantha mammosa ''Gasteracantha cancriformis'' (spinybacked orbweaver) is a species of orb-weaver spider (family Araneidae). It is widely distributed in the New World. The genus name ''Gasteracantha'' derives from the Greek words (', "belly") and (', "thorn" ...
'' spiderlings next to their eggs capsule Lycosidae female carrying young.jpg,
Wolf spider Wolf spiders are members of the family Lycosidae (). They are robust and agile hunters with excellent eyesight. They live mostly in solitude, hunt alone, and do not spin webs. Some are opportunistic hunters, pouncing upon prey as they find it or ...
carrying its young on its abdomen
Females lay up to 3,000 eggs in one or more silk egg sacs, which maintain a fairly constant
humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity dep ...
level. In some species, the females die afterwards, but females of other species protect the sacs by attaching them to their webs, hiding them in nests, carrying them in the chelicerae or attaching them to the
spinneret A spinneret is a silk-spinning organ of a spider or the larva of an insect. Some adult insects also have spinnerets, such as those borne on the forelegs of Embioptera. Spinnerets are usually on the underside of a spider's opisthosoma, and are ...
s and dragging them along. Baby spiders pass all their
larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. ...
l stages inside the egg sac and emerge as spiderlings, very small and sexually immature but similar in shape to adults. Some spiders care for their young, for example a
wolf spider Wolf spiders are members of the family Lycosidae (). They are robust and agile hunters with excellent eyesight. They live mostly in solitude, hunt alone, and do not spin webs. Some are opportunistic hunters, pouncing upon prey as they find it or ...
's brood clings to rough bristles on the mother's back, and females of some species respond to the "begging" behaviour of their young by giving them their prey, provided it is no longer struggling, or even regurgitate food. Like other
arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...
s, spiders have to molt to grow as their
cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...
("skin") cannot stretch.Ruppert, 523–24 In some species males mate with newly-molted females, which are too weak to be dangerous to the males. Most spiders live for only one to two years, although some
tarantula Tarantulas comprise a group of large and often hairy spiders of the family Theraphosidae. , 1,040 species have been identified, with 156 genera. The term "tarantula" is usually used to describe members of the family Theraphosidae, although m ...
s can live in captivity for over 20 years, and an Australian female trapdoor spider was documented to have lived in the wild for 43 years, dying of a parasitic wasp attack.


Size

Spiders occur in a large range of sizes. The smallest, '' Patu digua'' from Colombia, are less than in body length. The largest and heaviest spiders occur among
tarantula Tarantulas comprise a group of large and often hairy spiders of the family Theraphosidae. , 1,040 species have been identified, with 156 genera. The term "tarantula" is usually used to describe members of the family Theraphosidae, although m ...
s, which can have body lengths up to and leg spans up to .


Coloration

Only three classes of
pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compou ...
( ommochromes, bilins and
guanine Guanine () ( symbol G or Gua) is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine ( uracil in RNA). In DNA, guanine is paired with cytosine. The guanine nucleoside is ...
) have been identified in spiders, although other pigments have been detected but not yet characterized.
Melanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino ...
s,
carotenoid Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, ...
s and pterins, very common in other animals, are apparently absent. In some species, the exocuticle of the legs and prosoma is modified by a tanning process, resulting in a brown coloration. Bilins are found, for example, in '' Micrommata virescens'', resulting in its green color. Guanine is responsible for the white markings of the European garden spider '' Araneus diadematus''. It is in many species accumulated in specialized cells called guanocytes. In genera such as ''
Tetragnatha ''Tetragnatha'' is a genus of long-jawed orb-weavers found all over the world. It was first described by Pierre André Latreille in 1804, and it contains hundreds of species. Most occur in the tropics and subtropics, and many can run over wat ...
'', '' Leucauge'', '' Argyrodes'' or ''
Theridiosoma ''Theridiosoma'' is a genus of ray spiders that was first described by Octavius Pickard-Cambridge in 1879. They use their web as a high speed slingshot to actively hunt for prey. Description Mature spiders in this genus have a body length of 0 ...
'', guanine creates their silvery appearance. While guanine is originally an end-product of protein metabolism, its excretion can be blocked in spiders, leading to an increase in its storage. Structural colors occur in some species, which are the result of the diffraction, scattering or interference of light, for example by modified
seta In biology, setae (singular seta ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. ...
e or scales. The white prosoma of '' Argiope'' results from bristles reflecting the light, '' Lycosa'' and '' Josa'' both have areas of modified cuticle that act as light reflectors. The peacock spiders of Australia (genus ''
Maratus ''Maratus'' is a spider genus of the family Salticidae (jumping spiders). These spiders are commonly referred to as peacock spiders due to the males' colorful and usually iridescent patterns on the upper surface of the abdomen often enhanced with ...
'') are notable for their bright structural colours in the males. While in many spiders color is fixed throughout their lifespan, in some groups, color may be variable in response to environmental and internal conditions. Choice of prey may be able to alter the color of spiders. For example, the abdomen of '' Theridion grallator'' will become orange if the spider ingests certain species of
Diptera Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...
and adult
Lepidoptera Lepidoptera ( ) is an order of insects that includes butterflies and moths (both are called lepidopterans). About 180,000 species of the Lepidoptera are described, in 126 families and 46 superfamilies, 10 percent of the total described speci ...
, but if it consumes Homoptera or larval Lepidoptera, then the abdomen becomes green. Environmentally induced color changes may be morphological (occurring over several days) or physiological (occurring near instantly). Morphological changes require pigment synthesis and degradation. In contrast to this, physiological changes occur by changing the position of pigment-containing cells. An example of morphological color changes is background matching. ''
Misumena vatia ''Misumena vatia'' is a species of crab spider with a holarctic distribution. In North America, it is called the goldenrod crab spider or flower (crab) spider,Acorn, John and Sheldon, Ian. (2003). ''Bugs of Ontario'' Edmonton: Lone Pine Publish ...
'' for instance can change its body color to match the substrate it lives on which makes it more difficult to be detected by prey. An example of physiological color change is observed in ''
Cyrtophora cicatrosa ''Cyrtophora cicatrosa'', commonly known as the garden tent-web spider or dome spider, is a common species of orb-weavers found in many parts of Asia Asia (, ) is one of the world's most notable geographical regions, which is either con ...
'', which can change its body color from white to brown near instantly.


Ecology and behavior


Non-predatory feeding

Although spiders are generally regarded as predatory, the
jumping spider Jumping spiders are a group of spiders that constitute the family Salticidae. As of 2019, this family contained over 600 described genera and over 6,000 described species, making it the largest family of spiders at 13% of all species. Jumping spi ...
'' Bagheera kiplingi'' gets over 90% of its food from fairly solid plant material produced by
acacia ''Acacia'', commonly known as the wattles or acacias, is a large genus of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa and Australasia. The genus nam ...
s as part of a mutually beneficial relationship with a species of ant. Juveniles of some spiders in the families
Anyphaenidae Anyphaenidae is a family of araneomorph spiders, sometimes called anyphaenid sac spiders. They are distinguished from the sac spiders of the family Clubionidae and other spiders by having the abdominal spiracle placed one third to one half of the ...
, Corinnidae,
Clubionidae The sac spiders of the family Clubionidae have a very confusing taxonomic history. Once, this family was a large catch-all taxon for a disparate collection of spiders, similar only in that they had eight eyes arranged in two rows and conical anter ...
,
Thomisidae The Thomisidae are a family of spiders, including about 170 genera and over 2,100 species. The common name crab spider is often linked to species in this family, but is also applied loosely to many other families of spiders. Many members of th ...
and Salticidae feed on plant
nectar Nectar is a sugar-rich liquid produced by plants in glands called nectaries or nectarines, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualist ...
. Laboratory studies show that they do so deliberately and over extended periods, and periodically clean themselves while feeding. These spiders also prefer sugar solutions to plain water, which indicates that they are seeking nutrients. Since many spiders are nocturnal, the extent of nectar consumption by spiders may have been underestimated. Nectar contains
amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha ...
s,
lipid Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids in ...
s,
vitamin A vitamin is an organic molecule (or a set of molecules closely related chemically, i.e. vitamers) that is an essential micronutrient that an organism needs in small quantities for the proper functioning of its metabolism. Essential nutrie ...
s and minerals in addition to sugars, and studies have shown that other spider species live longer when nectar is available. Feeding on nectar avoids the risks of struggles with prey, and the costs of producing venom and digestive enzymes. Various species are known to feed on dead arthropods (scavenging), web silk, and their own shed exoskeletons.
Pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametop ...
caught in webs may also be eaten, and studies have shown that young spiders have a better chance of survival if they have the opportunity to eat pollen. In captivity, several spider species are also known to feed on
banana A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large herbaceous flowering plants in the genus ''Musa''. In some countries, bananas used for cooking may be called "plantains", disting ...
s, marmalade,
milk Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digest solid food. Immune factors and immune-modulat ...
,
egg yolk Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example be ...
and
sausage A sausage is a type of meat product usually made from ground meat—often pork, beef, or poultry—along with salt, spices and other flavourings. Other ingredients, such as grains or breadcrumbs may be included as fillers or extenders. ...
s.


Capturing prey

The best-known method of prey capture is by means of sticky webs. Varying placement of webs allows different species of spider to trap different insects in the same area, for example flat horizontal webs trap insects that fly up from vegetation underneath while flat vertical webs trap insects in horizontal flight. Web-building spiders have poor vision, but are extremely sensitive to vibrations. Females of the water spider '' Argyroneta aquatica'' build underwater "diving bell" webs that they fill with air and use for digesting prey, molting, mating and raising offspring. They live almost entirely within the bells, darting out to catch prey animals that touch the bell or the threads that anchor it. A few spiders use the surfaces of lakes and ponds as "webs", detecting trapped insects by the vibrations that these cause while struggling. Net-casting spiders weave only small webs, but then manipulate them to trap prey. Those of the genus '' Hyptiotes'' and the family
Theridiosomatidae The ray spiders (Theridiosomatidae) are a family of spiders first described by Eugène Simon in 1881. They are most recognizable for their construction of cone-shaped webs. The family contains several genera which actively hunt for prey by using ...
stretch their webs and then release them when prey strike them, but do not actively move their webs. Those of the family Deinopidae weave even smaller webs, hold them outstretched between their first two pairs of legs, and lunge and push the webs as much as twice their own body length to trap prey, and this move may increase the webs' area by a factor of up to ten. Experiments have shown that '' Deinopis spinosus'' has two different techniques for trapping prey: backwards strikes to catch flying insects, whose vibrations it detects; and forward strikes to catch ground-walking prey that it sees. These two techniques have also been observed in other deinopids. Walking insects form most of the prey of most deinopids, but one population of ''
Deinopis subrufa ''Asianopis subrufa'' (also called the rufous net-casting spider) is a species of net-casting spiders. It occurs in Australia (Queensland, New South Wales, Victoria and Tasmania) and in New Zealand. It is a nocturnal hunter, having excellent eye ...
'' appears to live mainly on tipulid flies that they catch with the backwards strike. Mature female
bolas spider A bolas spider is a member of the orb-weaver spider (family Araneidae) that, instead of spinning a typical orb web, hunts by using one or more sticky "capture blobs" on the end of a silk line, known as a " bolas". By swinging the bolas at flyin ...
s of the genus '' Mastophora'' build "webs" that consist of only a single "trapeze line", which they patrol. They also construct a bolas made of a single thread, tipped with a large ball of very wet sticky silk. They emit chemicals that resemble the pheromones of
moth Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order. There are thought to be approximately 160,000 species of moth, many of w ...
s, and then swing the bolas at the moths. Although they miss on about 50% of strikes, they catch about the same weight of insects per night as web-weaving spiders of similar size. The spiders eat the bolas if they have not made a kill in about 30 minutes, rest for a while, and then make new bolas. Juveniles and adult males are much smaller and do not make bolas. Instead they release different pheromones that attract moth flies, and catch them with their front pairs of legs. The primitive
Liphistiidae The spider family Liphistiidae, recognized by Tamerlan Thorell in 1869, comprises 8 genera and about 100 species of medium-sized spiders from Southeast Asia, China, and Japan. They are among the most basal living spiders, belonging to the subord ...
, the "trapdoor spiders" of the family
Ctenizidae Ctenizidae is a small family of mygalomorph spiders that construct burrows with a cork-like trapdoor made of soil, vegetation, and silk. They may be called trapdoor spiders, as are other, similar species, such as those of the families Liphistii ...
and many
tarantula Tarantulas comprise a group of large and often hairy spiders of the family Theraphosidae. , 1,040 species have been identified, with 156 genera. The term "tarantula" is usually used to describe members of the family Theraphosidae, although m ...
s are
ambush predator Ambush predators or sit-and-wait predators are carnivorous animals that capture or trap prey via stealth, luring or by (typically instinctive) strategies utilizing an element of surprise. Unlike pursuit predators, who chase to capture prey ...
s that lurk in burrows, often closed by trapdoors and often surrounded by networks of silk threads that alert these spiders to the presence of prey. Other ambush predators do without such aids, including many crab spiders, and a few species that prey on
bee Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyletic lineage within the superfami ...
s, which see
ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30  PHz) to 400 nm (750  THz), shorter than that of visible light, but longer than X-rays. UV radiation ...
, can adjust their ultraviolet reflectance to match the flowers in which they are lurking.
Wolf spider Wolf spiders are members of the family Lycosidae (). They are robust and agile hunters with excellent eyesight. They live mostly in solitude, hunt alone, and do not spin webs. Some are opportunistic hunters, pouncing upon prey as they find it or ...
s,
jumping spider Jumping spiders are a group of spiders that constitute the family Salticidae. As of 2019, this family contained over 600 described genera and over 6,000 described species, making it the largest family of spiders at 13% of all species. Jumping spi ...
s, fishing spiders and some
crab spider The Thomisidae are a family of spiders, including about 170 genera and over 2,100 species. The common name crab spider is often linked to species in this family, but is also applied loosely to many other families of spiders. Many members of thi ...
s capture prey by chasing it, and rely mainly on vision to locate prey. Some jumping spiders of the
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
''
Portia Portia may refer to: Biology * ''Portia'' (spider), a genus of jumping spiders *'' Anaea troglodyta'' or Portia, a brush-footed butterfly *Portia tree, a plant native to Polynesia Medication A form of birth control made of ethinylestradiol/lev ...
'' hunt other spiders in ways that seem intelligent, outflanking their victims or luring them from their webs. Laboratory studies show that ''Portia''s instinctive tactics are only starting points for a
trial-and-error Trial and error is a fundamental method of problem-solving characterized by repeated, varied attempts which are continued until success, or until the practicer stops trying. According to W.H. Thorpe, the term was devised by C. Lloyd Morgan (18 ...
approach from which these spiders learn very quickly how to overcome new prey species. However, they seem to be relatively slow "thinkers", which is not surprising, as their brains are vastly smaller than those of mammalian predators. Ant-mimicking spiders face several challenges: they generally develop slimmer abdomens and false "waists" in the
cephalothorax The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''cepha ...
to mimic the three distinct regions (tagmata) of an ant's body; they wave the first pair of legs in front of their heads to mimic antennae, which spiders lack, and to conceal the fact that they have eight legs rather than six; they develop large color patches round one pair of eyes to disguise the fact that they generally have eight simple eyes, while ants have two compound eyes; they cover their bodies with reflective bristles to resemble the shiny bodies of ants. In some spider species, males and females mimic different ant species, as female spiders are usually much larger than males. Ant-mimicking spiders also modify their behavior to resemble that of the target species of ant; for example, many adopt a zig-zag pattern of movement, ant-mimicking jumping spiders avoid jumping, and spiders of the genus '' Synemosyna'' walk on the outer edges of leaves in the same way as '' Pseudomyrmex''. Ant mimicry in many spiders and other arthropods may be for protection from predators that hunt by sight, including birds, lizards and spiders. However, several ant-mimicking spiders prey either on ants or on the ants' "
livestock Livestock are the domesticated animals raised in an agricultural setting to provide labor and produce diversified products for consumption such as meat, eggs, milk, fur, leather, and wool. The term is sometimes used to refer solely to ani ...
", such as
aphid Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...
s. When at rest, the ant-mimicking crab spider ''
Amyciaea ''Amyciaea'' is a genus of ant mimicking crab spiders that was first described by Eugène Louis Simon in 1885. They mimic weaver ants, their preferred prey. Description Spiders in this genus are generally around 5mm in length. They don't ha ...
'' does not closely resemble '' Oecophylla'', but while hunting it imitates the behavior of a dying ant to attract worker ants. After a kill, some ant-mimicking spiders hold their victims between themselves and large groups of ants to avoid being attacked.


Defense

There is strong evidence that spiders' coloration is
camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...
that helps them to evade their major predators,
bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
s and
parasitic wasp Parasitoid wasps are a large group of hymenopteran superfamilies, with all but the wood wasps (Orussoidea) being in the wasp-waisted Apocrita. As parasitoids, they lay their eggs on or in the bodies of other arthropods, sooner or later causi ...
s, both of which have good color vision. Many spider species are colored so as to merge with their most common backgrounds, and some have
disruptive coloration Disruptive coloration (also known as disruptive camouflage or disruptive patterning) is a form of camouflage that works by breaking up the outlines of an animal, soldier or military vehicle with a strongly contrasting pattern. It is often co ...
, stripes and blotches that break up their outlines. In a few species, such as the Hawaiian happy-face spider, '' Theridion grallator'', several coloration schemes are present in a ratio that appears to remain constant, and this may make it more difficult for predators to recognize the species. Most spiders are insufficiently dangerous or unpleasant-tasting for
warning coloration Aposematism is the advertising by an animal to potential predators that it is not worth attacking or eating. This unprofitability may consist of any defences which make the prey difficult to kill and eat, such as toxicity, venom, foul taste ...
to offer much benefit. However, a few species with powerful venom, large jaws or irritant bristles have patches of warning colors, and some actively display these colors when threatened. Many of the family
Theraphosidae Tarantulas comprise a group of large and often hairy spiders of the family Theraphosidae. , 1,040 species have been identified, with 156 genera. The term "tarantula" is usually used to describe members of the family Theraphosidae, although m ...
, which includes
tarantula Tarantulas comprise a group of large and often hairy spiders of the family Theraphosidae. , 1,040 species have been identified, with 156 genera. The term "tarantula" is usually used to describe members of the family Theraphosidae, although m ...
s and baboon spiders, have urticating hairs on their abdomens and use their legs to flick them at attackers. These bristles are fine
seta In biology, setae (singular seta ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. ...
e (bristles) with fragile bases and a row of barbs on the tip. The barbs cause intense irritation but there is no evidence that they carry any kind of venom. A few defend themselves against wasps by including networks of very robust threads in their webs, giving the spider time to flee while the wasps are struggling with the obstacles. The golden wheeling spider, ''
Carparachne aureoflava The wheel spider or golden wheel spider (''Carparachne aureoflava''), is a huntsman spider native to the Namib Desert of Southern Africa. This spider should not be confused with '' Leucorchestris arenicola'', a spider sharing the same common nam ...
'', of the Namibian desert escapes parasitic wasps by flipping onto its side and cartwheeling down sand
dune A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, f ...
s.


Socialization

A few spider species that build webs live together in large colonies and show social behavior, although not as complex as in
social insects Eusociality (from Greek εὖ ''eu'' "good" and social), the highest level of organization of sociality, is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping gen ...
. '' Anelosimus eximius'' (in the
family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
Theridiidae Theridiidae, also known as the tangle-web spiders, cobweb spiders and comb-footed spiders, is a large family of araneomorph spiders first described by Carl Jakob Sundevall in 1833. This diverse, globally distributed family includes over 3,000 sp ...
) can form colonies of up to 50,000 individuals. The genus ''Anelosimus'' has a strong tendency towards sociality: all known American species are social, and species in
Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Afric ...
are at least somewhat social. Members of other species in the same family but several different genera have independently developed social behavior. For example, although '' Theridion nigroannulatum'' belongs to a
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
with no other social species, ''T. nigroannulatum'' build colonies that may contain several thousand individuals that co-operate in prey capture and share food. Other communal spiders include several '' Philoponella'' species (family Uloboridae), '' Agelena consociata'' (family
Agelenidae The Agelenidae are a large family of spiders in the suborder Araneomorphae. Well-known examples include the common "grass spiders" of the genus ''Agelenopsis''. Nearly all Agelenidae are harmless to humans, but the bite of the hobo spider (''Era ...
) and '' Mallos gregalis'' (family Dictynidae). Social predatory spiders need to defend their prey against kleptoparasites ("thieves"), and larger colonies are more successful in this. The herbivorous spider '' Bagheera kiplingi'' lives in small colonies which help to protect eggs and spiderlings. Even widow spiders (genus '' Latrodectus''), which are notoriously cannibalistic, have formed small colonies in captivity, sharing webs and feeding together. In experiments, spider species like '' Steatoda grossa'', ''
Latrodectus hesperus ''Latrodectus hesperus'', the western black widow spider or western widow, is a venomous spider species found in western regions of North America. The female's body is 14–16 mm (1/2 in) in length and is black, often with an hourglass-shap ...
'' and ''
Eratigena agrestis The hobo spider (''Eratigena agrestis'', formerly ''Tegenaria agrestis'') is a member of the family of spiders known colloquially as funnel web spiders, but not to be confused with the Australian funnel-web spider. Individuals construct a funne ...
'' stayed away from ''
Myrmica rubra ''Myrmica rubra'', also known as the common red ant or erroneously the European fire ant, is a species of ant of the genus '' Myrmica'', found all over Europe and is now invasive in some parts of North America and Asia. It is mainly red in colou ...
'' ant colonies. These ants are predators and the pheromones they release for communication have a notable deterrent effect on these spider species.


Web types

There is no consistent relationship between the classification of spiders and the types of web they build: species in the same
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
may build very similar or significantly different webs. Nor is there much correspondence between spiders' classification and the chemical composition of their silks.
Convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
in web construction, in other words use of similar techniques by remotely related species, is rampant. Orb web designs and the spinning behaviors that produce them are the best understood. The basic radial-then-spiral sequence visible in orb webs and the sense of direction required to build them may have been inherited from the common ancestors of most spider groups. However, the majority of spiders build non-orb webs. It used to be thought that the sticky orb web was an evolutionary innovation resulting in the diversification of the Orbiculariae. Now, however, it appears that non-orb spiders are a subgroup that evolved from orb-web spiders, and non-orb spiders have over 40% more species and are four times as abundant as orb-web spiders. Their greater success may be because sphecid
wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder ...
s, which are often the dominant predators of spiders, much prefer to attack spiders that have flat webs.


Orb

About half the potential prey that hit orb webs escape. A web has to perform three functions: intercepting the prey (intersection), absorbing its
momentum In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass ...
without breaking (stopping), and trapping the prey by entangling it or sticking to it (retention). No single design is best for all prey. For example: wider spacing of lines will increase the web's area and hence its ability to intercept prey, but reduce its stopping power and retention; closer spacing, larger sticky droplets and thicker lines would improve retention, but would make it easier for potential prey to see and avoid the web, at least during the day. However, there are no consistent differences between orb webs built for use during the day and those built for use at night. In fact, there is no simple relationship between orb web design features and the prey they capture, as each orb-weaving species takes a wide range of prey. The hubs of orb webs, where the spiders lurk, are usually above the center, as the spiders can move downwards faster than upwards. If there is an obvious direction in which the spider can retreat to avoid its own predators, the hub is usually offset towards that direction. Horizontal orb webs are fairly common, despite being less effective at intercepting and retaining prey and more vulnerable to damage by rain and falling debris. Various researchers have suggested that horizontal webs offer compensating advantages, such as reduced vulnerability to wind damage; reduced visibility to prey flying upwards, because of the backlighting from the sky; enabling
oscillation Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendul ...
s to catch insects in slow horizontal flight. However, there is no single explanation for the common use of horizontal orb webs. Spiders often attach highly visible silk bands, called decorations or stabilimenta, to their webs. Field research suggests that webs with more decorative bands captured more prey per hour. However, a laboratory study showed that spiders reduce the building of these decorations if they sense the presence of predators. There are several unusual variants of orb web, many of them convergently evolved, including: attachment of lines to the surface of water, possibly to trap insects in or on the surface; webs with twigs through their centers, possibly to hide the spiders from predators; "ladderlike" webs that appear most effective in catching
moth Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order. There are thought to be approximately 160,000 species of moth, many of w ...
s. However, the significance of many variations is unclear. The orb-weaving species, ''
Zygiella x-notata ''Zygiella x-notata'', sometimes known as the missing sector orb weaver or the silver-sided sector spider,Factsheet 6: Missing-sector Orbweaver (Zygiella x-notata)', British Arachnological Society, 2016. Retrieved 27 November 2016 is a spider sp ...
,'' for example, is known for its characteristic missing sector orb web. The missing sector contains a signal thread used to detect prey vibrations on the female's web. In 1973, Skylab 3 took two orb-web spiders into
space Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually consi ...
to test their web-spinning capabilities in zero gravity. At first, both produced rather sloppy webs, but they adapted quickly.


Cobweb

Members of the family
Theridiidae Theridiidae, also known as the tangle-web spiders, cobweb spiders and comb-footed spiders, is a large family of araneomorph spiders first described by Carl Jakob Sundevall in 1833. This diverse, globally distributed family includes over 3,000 sp ...
weave irregular, tangled, three-dimensional webs, popularly known as cobwebs. There seems to be an evolutionary trend towards a reduction in the amount of sticky silk used, leading to its total absence in some species. The construction of cobwebs is less stereotyped than that of orb-webs, and may take several days.


Other

The Linyphiidae generally make horizontal but uneven sheets, with tangles of stopping threads above. Insects that hit the stopping threads fall onto the sheet or are shaken onto it by the spider, and are held by sticky threads on the sheet until the spider can attack from below.


Web design in zero gravity

Many experiments have been conducted to study the effect of zero gravity on the design of spider webs. In late 2020, reports of recent experiments were published that indicated that although web design was affected adversely in zero gravity conditions, having access to a light source could orient spiders and enable them to build their normally shaped webs under such conditions.


Evolution


Fossil record

Although the fossil record of spiders is considered poor, almost 1000 species have been described from fossils. Because spiders' bodies are quite soft, the vast majority of fossil spiders have been found preserved in
amber Amber is fossilized tree resin that has been appreciated for its color and natural beauty since Neolithic times. Much valued from antiquity to the present as a gemstone, amber is made into a variety of decorative objects."Amber" (2004). In M ...
. The oldest known amber that contains fossil arthropods dates from in the Early
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
period. In addition to preserving spiders' anatomy in very fine detail, pieces of amber show spiders mating, killing prey, producing silk and possibly caring for their young. In a few cases, amber has preserved spiders' egg sacs and webs, occasionally with prey attached; the oldest fossil web found so far is 100 million years old. Earlier spider fossils come from a few
lagerstätte A Lagerstätte (, from '' Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that exhibits extraordinary fossils with exceptional preservation—sometimes including preserved soft tissues. These f ...
n, places where conditions were exceptionally suited to preserving fairly soft tissues. The oldest known exclusively terrestrial arachnid is the trigonotarbid '' Palaeotarbus jerami'', from about in the
Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleoz ...
period, and had a triangular
cephalothorax The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''cepha ...
and segmented abdomen, as well as eight legs and a pair of pedipalps. ''
Attercopus ''Attercopus'' is an extinct genus of arachnids, containing one species ''Attercopus fimbriunguis'', known from flattened cuticle fossils from the Panther Mountain Formation in Upstate New York. It is placed in the extinct order Uraraneida, sp ...
fimbriunguis'', from in the
Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wh ...
period, bears the earliest known silk-producing spigots, and was therefore hailed as a spider at the time of its discovery. However, these spigots may have been mounted on the underside of the abdomen rather than on
spinneret A spinneret is a silk-spinning organ of a spider or the larva of an insect. Some adult insects also have spinnerets, such as those borne on the forelegs of Embioptera. Spinnerets are usually on the underside of a spider's opisthosoma, and are ...
s, which are modified
appendage An appendage (or outgrowth) is an external body part, or natural prolongation, that protrudes from an organism's body. In arthropods, an appendage refers to any of the homologous body parts that may extend from a body segment, including ante ...
s and whose mobility is important in the building of webs. Hence ''Attercopus'' and the similar
Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleo ...
arachnid '' Permarachne'' may not have been true spiders, and probably used silk for lining nests or producing egg cases rather than for building webs. The largest known fossil spider as of 2011 is the araneid '' Nephila jurassica'', from about , recorded from Daohuogo,
Inner Mongolia Inner Mongolia, officially the Inner Mongolia Autonomous Region, is an autonomous region of the People's Republic of China. Its border includes most of the length of China's border with the country of Mongolia. Inner Mongolia also accounts for a ...
in China. Its body length is almost 25 mm, (i.e., almost one inch). Several
Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferou ...
spiders were members of the
Mesothelae The Mesothelae are a suborder of spiders (order Araneae) that includes a single extant family, Liphistiidae, and a number of extinct families. This suborder is thought to form the sister group to all other living spiders, and to retain ancestral ...
, a primitive group now represented only by the
Liphistiidae The spider family Liphistiidae, recognized by Tamerlan Thorell in 1869, comprises 8 genera and about 100 species of medium-sized spiders from Southeast Asia, China, and Japan. They are among the most basal living spiders, belonging to the subord ...
. The mesothelid '' Paleothele montceauensis'', from the Late
Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferou ...
over , had five spinnerets. Although the
Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleo ...
period saw rapid
diversification Diversification may refer to: Biology and agriculture * Genetic divergence, emergence of subpopulations that have accumulated independent genetic changes * Agricultural diversification involves the re-allocation of some of a farm's resources to n ...
of flying
insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...
s, there are very few fossil spiders from this period. The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appear in the
Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest per ...
well before . Some Triassic mygalomorphs appear to be members of the family Hexathelidae, whose modern members include the notorious Sydney funnel-web spider, and their spinnerets appear adapted for building funnel-shaped webs to catch jumping insects. Araneomorphae account for the great majority of modern spiders, including those that weave the familiar orb-shaped webs. The
Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...
and
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
periods provide a large number of fossil spiders, including representatives of many modern families.


External relationships

The spiders (Araneae) are monophyletic (i.e., a
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...
, consisting of a last common ancestor and all of its descendants). There has been debate about what their closest evolutionary relatives are, and how all of these evolved from the ancestral
chelicerate The subphylum Chelicerata (from New Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. It contains the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks, and mite ...
s, which were marine animals. This 2019 cladogram illustrates the spiders' phylogenetic relationships. Arachnids lack some features of other chelicerates, including backward-pointing mouths and gnathobases ("jaw bases") at the bases of their legs; both of these features are part of the ancestral
arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...
feeding system. Instead, they have mouths that point forwards and downwards, and all have some means of breathing air. Spiders (Araneae) are distinguished from other arachnid groups by several characteristics, including
spinneret A spinneret is a silk-spinning organ of a spider or the larva of an insect. Some adult insects also have spinnerets, such as those borne on the forelegs of Embioptera. Spinnerets are usually on the underside of a spider's opisthosoma, and are ...
s and, in males, pedipalps that are specially adapted for sperm transfer.


Internal relationships

The
cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...
shows the relation among spider suborders and families:


Taxonomy

The order name Araneae derives from
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
''aranea'' borrowing
Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic pe ...
''arákhnē'' from ''arákhnēs''. Spiders are divided into two suborders,
Mesothelae The Mesothelae are a suborder of spiders (order Araneae) that includes a single extant family, Liphistiidae, and a number of extinct families. This suborder is thought to form the sister group to all other living spiders, and to retain ancestral ...
and Opisthothelae, of which the latter contains two infraorders, Mygalomorphae and Araneomorphae. Some 50,356 living
species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...
of spiders (order Araneae) have been identified, grouped into 132 families and 4,280
genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...
by
arachnologists Arachnology is the scientific study of arachnids, which comprise spiders and related invertebrates such as scorpions, pseudoscorpions, and harvestmen. Those who study spiders and other arachnids are arachnologists. More narrowly, the study of sp ...
in 2022.


Mesothelae

The only living members of the primitive Mesothelae are the family
Liphistiidae The spider family Liphistiidae, recognized by Tamerlan Thorell in 1869, comprises 8 genera and about 100 species of medium-sized spiders from Southeast Asia, China, and Japan. They are among the most basal living spiders, belonging to the subord ...
, found only in
Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainland ...
,
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
, and
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...
. Most of the Liphistiidae construct silk-lined burrows with thin trapdoors, although some species of the genus '' Liphistius'' build camouflaged silk tubes with a second trapdoor as an emergency exit. Members of the genus ''Liphistius'' run silk "
tripwire A tripwire is a passive triggering mechanism. Typically, a wire or cord is attached to a device for detecting or reacting to physical movement. Military applications Such tripwires may be attached to one or more mines – especially fragme ...
s" outwards from their tunnels to help them detect approaching prey, while those of the genus '' Heptathela'' do not and instead rely on their built-in vibration sensors. Spiders of the genus ''Heptathela'' have no venom glands, although they do have venom gland outlets on the fang tip. Full text at The extinct families Arthrolycosidae, found in
Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferou ...
and
Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleo ...
rocks, and Arthromygalidae, so far found only in
Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferou ...
rocks, have been classified as members of the Mesothelae.


Mygalomorphae

The Mygalomorphae, which first appeared in the
Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest per ...
period, are generally heavily built and ″hairy″, with large, robust chelicerae and fangs (technically, spiders do not have true
hairs Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and fine ...
, but rather
setae In biology, setae (singular seta ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. ...
). Well-known examples include
tarantula Tarantulas comprise a group of large and often hairy spiders of the family Theraphosidae. , 1,040 species have been identified, with 156 genera. The term "tarantula" is usually used to describe members of the family Theraphosidae, although m ...
s, ctenizid trapdoor spiders and the
Australasian funnel-web spider Atracidae is a family of mygalomorph spiders, commonly known as Australian funnel-web spiders or atracids. It has been included as a subfamily of the Hexathelidae, but is now recognized as a separate family. All members of the family are native to ...
s. Most spend the majority of their time in burrows, and some run silk tripwires out from these, but a few build webs to capture prey. However, mygalomorphs cannot produce the pirifom silk that the Araneomorphae use as an instant adhesive to glue silk to surfaces or to other strands of silk, and this makes web construction more difficult for mygalomorphs. Since mygalomorphs rarely "
balloon A balloon is a flexible bag that can be inflated with a gas, such as helium, hydrogen, nitrous oxide, oxygen, and air. For special tasks, balloons can be filled with smoke, liquid water, granular media (e.g. sand, flour or rice), or lig ...
" by using air currents for transport, their populations often form clumps. In addition to arthropods, some mygalomorphs are known to prey on frogs, small mammals, lizards, snakes, snails, and small birds.


Araneomorphae

In addition to accounting for over 90% of spider species, the Araneomorphae, also known as the "true spiders", include
orb-web spider Orb-weaver spiders are members of the spider family Araneidae. They are the most common group of builders of spiral wheel-shaped webs often found in gardens, fields, and forests. The English word "orb" can mean "circular", hence the English na ...
s, the
cursorial A cursorial organism is one that is adapted specifically to run. An animal can be considered cursorial if it has the ability to run fast (e.g. cheetah) or if it can keep a constant speed for a long distance (high endurance). "Cursorial" is often u ...
wolf spider Wolf spiders are members of the family Lycosidae (). They are robust and agile hunters with excellent eyesight. They live mostly in solitude, hunt alone, and do not spin webs. Some are opportunistic hunters, pouncing upon prey as they find it or ...
s, and
jumping spider Jumping spiders are a group of spiders that constitute the family Salticidae. As of 2019, this family contained over 600 described genera and over 6,000 described species, making it the largest family of spiders at 13% of all species. Jumping spi ...
s, as well as the only known herbivorous spider, '' Bagheera kiplingi''. They are distinguished by having fangs that oppose each other and cross in a pinching action, in contrast to the Mygalomorphae, which have fangs that are nearly parallel in alignment.


Human interaction


Media coverage and misconceptions

Information about spiders in the media is often emphasizing how dangerous and unpleasant they are. A recent study investigated the global spread of (mis-)information on spiders using a high-resolution global database of online newspaper articles on spider–human interactions. These reports covered stories of spider–human encounters and bites published from 2010–2020. The study found that 47% of articles contained errors and 43% were sensationalist.


Bites

Although spiders are widely feared, only a few species are dangerous to people. Spiders will only bite humans in self-defense, and few produce worse effects than a mosquito bite or bee sting. Most of those with medically serious bites, such as
recluse spider The recluse spiders (''Loxosceles'' (), also known as brown spiders, fiddle-backs, violin spiders, and reapers, is a genus of spiders that was first described by R. T. Lowe in 1832. They are venomous spiders known for their bite, which sometimes ...
s (genus ''Loxosceles'') and widow spiders (genus '' Latrodectus''), would rather flee and bite only when trapped, although this can easily arise by accident. The defensive tactics of
Australian funnel-web spider Atracidae is a family of mygalomorph spiders, commonly known as Australian funnel-web spiders or atracids. It has been included as a subfamily of the Hexathelidae, but is now recognized as a separate family. All members of the family are native to ...
s (family Atracidae) include fang display. Their venom, although they rarely inject much, has resulted in 13 attributed human deaths over 50 years. They have been deemed to be the world's most dangerous spiders on clinical and venom toxicity grounds, though this claim has also been attributed to the Brazilian wandering spider (genus ''
Phoneutria ''Phoneutria'' is a genus of spiders in the family Ctenidae. Phoneutria venom is potentially medically significant to humans. They are mainly found in northern South America, with one species in Central America. Members of the genus are commo ...
''). There were about 100 reliably reported deaths from spider bites in the 20th century, compared to about 1,500 from
jellyfish Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbre ...
stings. Many alleged cases of spider bites may represent incorrect diagnoses, which would make it more difficult to check the effectiveness of treatments for genuine bites. A review published in 2016 agreed with this conclusion, showing that 78% of 134 published medical case studies of supposed spider bites did not meet the necessary criteria for a spider bite to be verified. In the case of the two genera with the highest reported number of bites, ''Loxosceles'' and '' Latrodectus'', spider bites were not verified in over 90% of the reports. Even when verification had occurred, details of the treatment and its effects were often lacking.


Silk

Because
spider silk Spider silk is a protein fibre spun by spiders. Spiders use their silk to make webs or other structures, which function as sticky nets to catch other animals, or as nests or cocoons to protect their offspring, or to wrap up prey. They can ...
is both light and very strong, attempts are being made to produce it in
goat The goat or domestic goat (''Capra hircus'') is a domesticated species of goat-antelope typically kept as livestock. It was domesticated from the wild goat (''C. aegagrus'') of Southwest Asia and Eastern Europe. The goat is a member of the a ...
s' milk and in the leaves of plants, by means of
genetic engineering Genetic engineering, also called genetic modification or genetic manipulation, is the modification and manipulation of an organism's genes using technology. It is a set of technologies used to change the genetic makeup of cells, including ...
.


Arachnophobia

Arachnophobia Arachnophobia is a specific phobia brought about by the irrational fear of spiders and other arachnids such as scorpions. Signs and symptoms People with arachnophobia tend to feel uneasy in any area they believe could harbour spiders or that ...
is a specific phobia—it is the abnormal fear of spiders or anything reminiscent of spiders, such as webs or spiderlike shapes. It is one of the most common specific phobias, and some statistics show that 50% of women and 10% of men show symptoms. It may be an exaggerated form of an
instinct Instinct is the inherent inclination of a living organism towards a particular complex behaviour, containing both innate (inborn) and learned elements. The simplest example of an instinctive behaviour is a fixed action pattern (FAP), in which a v ...
ive response that helped early humans to survive, or a cultural phenomenon that is most common in predominantly European societies.


As food

Spiders are used as food. Cooked
tarantula Tarantulas comprise a group of large and often hairy spiders of the family Theraphosidae. , 1,040 species have been identified, with 156 genera. The term "tarantula" is usually used to describe members of the family Theraphosidae, although m ...
s are considered a delicacy in
Cambodia Cambodia (; also Kampuchea ; km, កម្ពុជា, UNGEGN: ), officially the Kingdom of Cambodia, is a country located in the southern portion of the Indochinese Peninsula in Southeast Asia, spanning an area of , bordered by Thailand ...
, and by the Piaroa Indians of southern
Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...
 – provided the highly irritant bristles, the spiders' main defense system, are removed first.


Spiders in culture

Spiders have been the focus of stories and mythologies of various cultures for centuries.
Uttu Uttu was a Mesopotamian goddess of Sumerian origin. She was associated with weaving. She appears in multiple myths, such as ''Enki and Ninhursag'' and ''Enki and the World Order''. Name and character Uttu's name was written TAG×TÙG, with the ...
, the ancient Sumerian goddess of weaving, was envisioned as a spider spinning her web. According to her main myth, she resisted her father
Enki , image = Enki(Ea).jpg , caption = Detail of Enki from the Adda Seal, an ancient Akkadian cylinder seal dating to circa 2300 BC , deity_of = God of creation, intelligence, crafts, water, seawater, lakewater, fertility, semen, magic, mischief ...
's sexual advances by ensconcing herself in her web, but let him in after he promised her fresh
produce Produce is a generalized term for many farm-produced crops, including fruits and vegetables ( grains, oats, etc. are also sometimes considered ''produce''). More specifically, the term ''produce'' often implies that the products are fres ...
as a marriage gift, thereby allowing him to intoxicate her with
beer Beer is one of the oldest and the most widely consumed type of alcoholic drink in the world, and the third most popular drink overall after water and tea. It is produced by the brewing and fermentation of starches, mainly derived from ce ...
and
rape Rape is a type of sexual assault usually involving sexual intercourse or other forms of sexual penetration carried out against a person without their consent. The act may be carried out by physical force, coercion, abuse of authority, or ...
her. Enki's wife
Ninhursag , deity_of=Mother goddess, goddess of fertility, mountains, and rulers , image= Mesopotamian - Cylinder Seal - Walters 42564 - Impression.jpg , caption= Akkadian cylinder seal impression depicting a vegetation goddess, possibly Ninhursag, sitt ...
heard Uttu's screams and rescued her, removing Enki's
semen Semen, also known as seminal fluid, is an organic bodily fluid created to contain spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize the female ovum. Sem ...
from her
vagina In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the vestibule to the cervix. The outer vaginal opening is normally partly covered by a thin layer of mucosal tissue called the hymen ...
and planting it in the ground to produce eight previously-nonexistent plants. In a story told by the Roman poet
Ovid Pūblius Ovidius Nāsō (; 20 March 43 BC – 17/18 AD), known in English as Ovid ( ), was a Augustan literature (ancient Rome), Roman poet who lived during the reign of Augustus. He was a contemporary of the older Virgil and Horace, with whom ...
in his ''
Metamorphoses The ''Metamorphoses'' ( la, Metamorphōsēs, from grc, μεταμορφώσεις: "Transformations") is a Latin narrative poem from 8 CE by the Roman poet Ovid. It is considered his '' magnum opus''. The poem chronicles the history of the ...
'', Arachne (Ancient Greek for "spider") was a Lydian girl who challenged the goddess
Athena Athena or Athene, often given the epithet Pallas, is an ancient Greek goddess associated with wisdom, warfare, and handicraft who was later syncretized with the Roman goddess Minerva. Athena was regarded as the patron and protectress of v ...
to a weaving contest. Arachne won, but Athena destroyed her tapestry out of jealousy, causing Arachne to hang herself. In an act of mercy, Athena brought Arachne back to life as the first spider. Stories about the
trickster In mythology and the study of folklore and religion, a trickster is a character in a story ( god, goddess, spirit, human or anthropomorphisation) who exhibits a great degree of intellect or secret knowledge and uses it to play tricks or otherwi ...
-spider Anansi are prominent in the
folktale A folktale or folk tale is a folklore genre that typically consists of a story passed down from generation to generation orally. Folktale may also refer to: Categories of stories * Folkloric tale from oral tradition * Fable (written form of the a ...
s of
West Africa West Africa or Western Africa is the westernmost region of Africa. The United Nations defines Western Africa as the 16 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Mali ...
and the
Caribbean The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean ...
. In some cultures, spiders have symbolized patience due to their hunting technique of setting webs and waiting for prey, as well as mischief and malice due to their venomous bites. The Italian
tarantella () is a group of various southern Italian folk dances originating in the regions of Calabria, Campania and Puglia. It is characterized by a fast upbeat tempo, usually in time (sometimes or ), accompanied by tambourines. It is among the mo ...
is a dance to rid the young woman of the lustful effects of a spider bite. Web-spinning also caused the association of the spider with creation myths, as they seem to have the ability to produce their own worlds. Dreamcatchers are depictions of spiderwebs. The Moche people of ancient
Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = National seal , national_motto = "Firm and Happy f ...
worshipped nature. They placed emphasis on animals and often depicted spiders in their art.Berrin, Katherine & Larco Museum. ''The Spirit of Ancient Peru: Treasures from the Museo Arqueológico Rafael Larco Herrera''. New York:
Thames and Hudson Thames & Hudson (sometimes T&H for brevity) is a publisher of illustrated books in all visually creative categories: art, architecture, design, photography, fashion, film, and the performing arts. It also publishes books on archaeology, history, ...
, 1997.


See also

*
Arachnidism A spider bite, also known as arachnidism, is an injury resulting from the bite of a spider. The effects of most bites are not serious. Most bites result in mild symptoms around the area of the bite. Rarely they may produce a necrotic skin wound ...
*
Glossary of spider terms This glossary describes the terms used in formal descriptions of spiders; where applicable these terms are used in describing other arachnids. Links within the glossary are shown . Terms A Abdomen or opisthosoma: One of the two main body part ...
* List of animals that produce silk * List of endangered spiders * Spider taxonomy *
Toxins A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849� ...


Citations


General and cited references

* *


Further reading

* * * * * * *


External links

*
Picture story about the jumping spider ''Aelurillus v-insignitus''

New Mexico State University "The Spiders of the Arid Southwest"


* [https://web.archive.org/web/20110511234340/http://media.library.uiuc.edu/cgi/b/bib/bix-idx?type=simple&c=bix&sid=54d8a20e4f1eb5f2de074bad4caba7ae&Submit=search&sort=title&q1=spiders&rgn1=Entire+record list of field guides to spiders], from the International Field Guides database *
Record breaking achievements by spiders and the scientists who study them
{{Authority control Articles containing video clips Carboniferous arachnids Extant Pennsylvanian first appearances Taxa named by Carl Alexander Clerck