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 ...
of
arachnid
Arachnida () is a class of joint-legged invertebrate animals (arthropods), in the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, harvestmen, camel spiders, whip spiders and vinegaro ...
s
colloquially
Colloquialism (), also called colloquial language, everyday language or general parlance, is the linguistic style used for casual (informal) communication. It is the most common functional style of speech, the idiom normally employed in convers ...
known as harvestmen, harvesters, harvest spiders, or daddy longlegs. , over 6,650 species of harvestmen have been discovered worldwide, although the total number of
extant
Extant is the opposite of the word extinct. It may refer to:
* Extant hereditary titles
* Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English
* Extant taxon, a taxon which is not extin ...
species may exceed 10,000. The order Opiliones includes five suborders:
Cyphophthalmi
Cyphophthalmi is a suborder of harvestmen, colloquially known as mite harvestmen. Cyphophthalmi comprises 36 genera, and more than two hundred described species. The six families are currently grouped into three infraorders: the Boreophthalmi, Sc ...
,
Eupnoi
The Eupnoi are a suborder of harvestmen, with more than 200 genera, and about 1,700 described species.
They consist of two superfamilies, the Phalangioidea with many long-legged species common to northern temperate regions, and the small group C ...
,
Dyspnoi
Dyspnoi is a suborder of harvestmen, currently comprising 43 extant genera and 356 extant species, although more species are expected to be described in the future. The eight families are currently grouped into three superfamilies: the Acropsopil ...
,
Laniatores
Laniatores is the largest suborder of the arachnid order Opiliones with over 4,000 described species worldwide. The majority of the species are highly dependent on humid environments and usually correlated with tropical and temperate forest habit ...
, and Tetrophthalmi, which were named in 2014.
Representatives of each extant suborder can be found on all continents except
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 contine ...
.
Well-preserved fossils have been found in the 400-million-year-old
Rhynie chert
The Rhynie chert is a Lower Devonian sedimentary deposit exhibiting extraordinary fossil detail or completeness (a Lagerstätte). It is exposed near the village of Rhynie, Aberdeenshire, Scotland; a second unit, the Windyfield chert, is located ...
s of Scotland, and 305-million-year-old rocks in France. These fossils look surprisingly modern, indicating that their basic body shape developed very early on, and, at least in some taxa, has changed little since that time.
Their
phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
position within the Arachnida is disputed; their closest relatives may be the mites (
Acari
Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear evid ...
Pseudoscorpiones
Pseudoscorpions, also known as false scorpions or book scorpions, are small, scorpion-like arachnids belonging to the order Pseudoscorpiones, also known as Pseudoscorpionida or Chelonethida.
Pseudoscorpions are generally beneficial to humans sin ...
, and
Solifugae
Solifugae is an order of animals in the class Arachnida known variously as camel spiders, wind scorpions, sun spiders, or solifuges. The order includes more than 1,000 described species in about 147 genera. Despite the common names, they are ne ...
). Although superficially similar to and often misidentified as spiders (order
Araneae
Spiders ( order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species dive ...
), the Opiliones are a distinct order that is not closely related to spiders. They can be easily distinguished from long-legged spiders by their fused body regions and single pair of eyes in the middle of 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 ...
. Spiders have a distinct abdomen that is separated from the cephalothorax by a constriction, and they have three to four pairs of eyes, usually around the margins of the cephalothorax.
English speakers may colloquially refer to species of Opiliones as "daddy longlegs" or "granddaddy longlegs", but this name is also used for two other distantly related groups of
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 chitin, o ...
s, the
crane flies
Crane fly is a common name referring to any member of the insect family Tipulidae. Cylindrotominae, Limoniinae, and Pediciinae have been ranked as subfamilies of Tipulidae by most authors, though occasionally elevated to family rank. In the most ...
of the family Tipulidae, and the cellar spiders of the family Pholcidae, most likely because of their similar appearance. Harvestmen are also referred to as "shepherd spiders" in reference to how their unusually long legs reminded observers of the ways that some European shepherds used stilts to better observe their wandering flocks from a distance.
Description
The Opiliones are known for having exceptionally long legs relative to their body size; however, some species are short-legged. As in all Arachnida, the body in the Opiliones has two tagmata, the
anterior
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
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 ...
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 torso. ...
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 ...
. The most easily discernible difference between harvestmen and spiders is that in harvestmen, the connection between the cephalothorax and abdomen is broad, so that the body appears to be a single oval structure. Other differences include the fact that Opiliones have no venom glands in their
chelicerae
The chelicerae () are the mouthparts of the subphylum Chelicerata, an arthropod group that includes arachnids, horseshoe crabs, and sea spiders. Commonly referred to as " jaws", chelicerae may be shaped as either articulated fangs, or similarl ...
, so pose no danger to humans.
They also have no silk glands and therefore do not build webs. In some highly derived species, the first five abdominal segments are fused into a
dorsal
Dorsal (from Latin ''dorsum'' ‘back’) may refer to:
* Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism
* Dorsal, positioned on top of an aircraft's fuselage
* Dorsal co ...
shield called the
scutum
The ''scutum'' (; plural ''scuta'') was a type of shield used among Italic peoples in antiquity, most notably by the army of ancient Rome starting about the fourth century BC.
The Romans adopted it when they switched from the military formatio ...
, which in most such species is fused with the
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 under ...
. Some such Opiliones only have this shield in the males. In some species, the two posterior abdominal segments are reduced. Some of them are divided medially on the surface to form two plates beside each other. The second pair of legs is longer than the others and function as antennae or feelers. In short-legged species, this may not be obvious.
The feeding apparatus (
stomotheca Stomotheca is the term applied to the feeding apparatus in front of the mouth of harvestmen, and sometimes the related scorpions. Usually it consists of the ''epistome'' (labrum), two pairs of ''coxapophyses'' (endites, maxillary lobes) and often a ...
) differs from most arachnids in that Opiliones can swallow chunks of solid food, not only liquids. The stomotheca is formed by extensions of the coxae of the pedipalps and the first pair of legs.
Most Opiliones, except for Cyphophthalmi, have a single pair of eyes in the middle of the head, oriented sideways. Eyes in Cyphophthalmi, when present, are located laterally, near the ozopores. A 305-million-year-old fossilized harvestman with two pairs of eyes was reported in 2014. This find indicates that the eyes in Cyphophthalmi are not homologous to the eyes of other harvestmen. However, some species are eyeless, such as the Brazilian '' Caecobunus termitarum'' (
Grassatores
The Grassatores are the most diverse infraorder of the Laniatores. It includes over 3,500 species distributed mainly in the tropics
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropi ...
) from
termite
Termites are small insects that live in colonies and have distinct castes (eusocial) and feed on wood or other dead plant matter. Termites comprise the infraorder Isoptera, or alternatively the epifamily Termitoidae, within the order Blattode ...
Gonyleptidae
Gonyleptidae is a neotropical family of harvestmen (Order Opiliones) with more than 800 species, the largest in the Suborder Laniatores and the second largest of the Opiliones as a whole. The largest known harvestmen are gonyleptids.
Like most h ...
) from caves, most species of Cyphophthalmi, and all species of the Guasiniidae.
Harvestmen have a pair of prosomatic defensive scent glands (
ozopore
An ozopore is the opening of a defensive gland present in some arthropods, notably in millipedes of the order Polydesmidaquinones
The quinones are a class of organic compounds that are formally "derived from aromatic compounds uch as benzene or naphthalene">benzene.html" ;"title="uch as benzene">uch as benzene or naphthalene] by conversion of an even number of –CH= grou ...
. They do not have
book lungs
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 ...
, and breathe through
tracheae
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 the la ...
. A pair of spiracles is located between the base of the fourth pair of legs and the abdomen, with one opening on each side. In more active species, spiracles are also found upon the tibia of the legs. They have a gonopore on the ventral cephalothorax, and the copulation is direct as male Opiliones have a penis, unlike other arachnids. All species lay
eggs
Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...
.
Typical body length does not exceed , and some species are smaller than 1 mm, although the largest known species, '' Trogulus torosus'' (
Trogulidae
Trogulidae is a family of harvestmen with 5 genera and 57 extant species and one fossil species.
Members of this species have short legs and live in soil. They have dirt attached to their bodies, to escape predators. Their body length ranges fr ...
), grows as long as . The leg span of many species is much greater than the body length and sometimes exceeds and to in Southeast Asia. Most species live for a year.
Behavior
Many species are
omnivorous
An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nut ...
, eating primarily small insects and all kinds of plant material and fungi. Some are scavengers, feeding upon dead organisms, bird dung, and other
fecal
Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...
material. Such a broad range is unusual in arachnids, which are typically pure predators. Most hunting harvestmen ambush their prey, although active hunting is also found. Because their eyes cannot form images, they use their second pair of legs as antennae to explore their environment. Unlike most other arachnids, harvestmen do not have a sucking stomach or a filtering mechanism. Rather, they ingest small particles of their food, thus making them vulnerable to internal parasites such as
gregarine
The gregarines are a group of Apicomplexan alveolates, classified as the Gregarinasina or Gregarinia. The large (roughly half a millimeter) parasites inhabit the intestines of many invertebrates. They are not found in any vertebrates. However, gr ...
s.
Although
parthenogenetic
Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development ...
species do occur, most harvestmen reproduce sexually. Mating involves direct copulation, rather than the deposition of a
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 ...
. The males of some species offer a secretion (nuptial gift) from their chelicerae to the female before copulation. Sometimes, the male guards the female after copulation, and in many species, the males defend territories. In some species, males also exhibit post-copulatory behavior in which the male specifically seeks out and shakes the female's sensory leg. This is believed to entice the female into mating a second time.
The females lay eggs from an ovipositor shortly after mating to several months later. Some species build nests for this purpose. A unique feature of harvestmen is that some species practice parental care, in which the male is solely responsible for guarding the eggs resulting from multiple partners, often against egg-eating females, and cleaning the eggs regularly. Depending on circumstances such as temperature, the eggs may hatch at any time after the first 20 days, up to about half a year after being laid. Harvestmen variously pass through four to eight nymphal instars to reach maturity, with most known species having six instars.
Most species are
nocturnal
Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite.
Nocturnal creatures generally have highly developed sens ...
and colored in hues of brown, although a number of diurnal species are known, some of which have vivid patterns in yellow, green, and black with varied reddish and blackish mottling and reticulation.
Many species of harvestmen easily tolerate members of their own species, with aggregations of many individuals often found at protected sites near water. These aggregations may number 200 individuals in the
Laniatores
Laniatores is the largest suborder of the arachnid order Opiliones with over 4,000 described species worldwide. The majority of the species are highly dependent on humid environments and usually correlated with tropical and temperate forest habit ...
, and more than 70,000 in certain
Eupnoi
The Eupnoi are a suborder of harvestmen, with more than 200 genera, and about 1,700 described species.
They consist of two superfamilies, the Phalangioidea with many long-legged species common to northern temperate regions, and the small group C ...
. Gregarious behavior is likely a strategy against climatic odds, but also against predators, combining the effect of scent secretions, and reducing the probability of any particular individual being eaten.
Harvestmen clean their legs after eating by drawing each leg in turn through their jaws.
Antipredator defenses
Predators of harvestmen include a variety of animals, including some mammals, amphibians, and other arachnids like spiders and scorpions. Opiliones display a variety of primary and secondary defenses against predation, ranging from morphological traits such as body armor to behavioral responses to chemical secretions. Some of these defenses have been attributed and restricted to specific groups of harvestmen.
Primary defenses
Primary defenses help the harvestmen avoid encountering a potential predator, and include
crypsis
In ecology, crypsis is the ability of an animal or a plant to avoid observation or detection by other animals. It may be a predation strategy or an antipredator adaptation. Methods include camouflage, nocturnality, subterranean lifestyle and m ...
,
aposematism
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 or ...
Particular patterns or color markings on harvestmen's bodies can reduce detection by disrupting the animals' outlines or providing camouflage. Markings on legs can cause an interruption of the leg outline and loss of leg proportion recognition. Darker colorations and patterns function as
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 ...
when they remain motionless.Gnaspini, P., Cavalheiro, A.J., 1998. Chemical and Behavioral Defenses of a Neotropical Cavernicolous Harvestman: Goniosoma spelaeum (Opiliones, Laniatores, Gonyleptidae). J. Arachnol. 26, 81–90. Within the genus ''
Leiobunum
''Leiobunum'' is a genus of the harvestman family Sclerosomatidae with more than 100 described species. Contrary to popular belief, they are not spiders, although they share a resemblance. They are arachnids, in the order Opiliones, harvestmen. ...
'' are multiple species with cryptic coloration that changes over ontogeny to match the
microhabitat
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 ...
used at each life stage. Many species have also been able to camouflage their bodies by covering with secretions and debris from the leaf litter found in their environments. Some hard-bodied harvestmen have
epizoic
An epibiont (from the Ancient Greek meaning "living on top of") is an organism that lives on the surface of another living organism, called the basibiont ("living underneath"). The interaction between the two organisms is called epibiosis. An ep ...
cyanobacteria and liverworts growing on their bodies that suggest potential benefits for camouflage against large backgrounds to avoid detection by diurnal predators.
Aposematism and mimicry
Some harvestmen have elaborate and brightly colored patterns or appendages which contrast with the body coloration, potentially serving as an aposematic warning to potential predators.González, A., Rossini, C., Eisner, T., 2004. Mimicry: imitative depiction of discharged defensive secretion on carapace of an opilionid. CHEMOECOLOGY 14, 5–7.Pomini, A.M., Machado, G., Pinto-da-Rocha, R., Macías-Ordóñez, R., Marsaioli, A.J., 2010. Lines of defense in the harvestman Hoplobunus mexicanus (Arachnida: Opiliones): Aposematism, stridulation, thanatosis, and irritant chemicals. Biochem. Syst. Ecol. 38, 300–308. This mechanism is thought to be commonly used during daylight, when they could be easily seen by any predators.
Other harvestmen may exhibit mimicry to resemble other species’ appearances. Some Gonyleptidae individuals that produce translucid secretions have orange markings on their
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 under ...
s. This may have an aposematic role by mimicking the coloration of glandular emissions of two other quinone-producing species. Mimicry (
Müllerian mimicry
Müllerian mimicry is a natural phenomenon in which two or more well-defended species, often foul-tasting and sharing common predators, have come to mimic each other's honest warning signals, to their mutual benefit. The benefit to Müllerian ...
) occurring between Brazilian harvestmen that resemble others could be explained by convergent evolution.
Secondary defenses
Secondary defenses allow for harvestmen to escape and survive from a predator after direct or indirect contact, including
thanatosis
Apparent death, colloquially known as playing dead, feigning death, or playing possum, is a behavior in which animals take on the appearance of being dead. It is an immobile state most often triggered by a predatory attack and can be found in a ...
,
freezing
Freezing is a phase transition where a liquid turns into a solid when its temperature is lowered below its freezing point. In accordance with the internationally established definition, freezing means the solidification phase change of a liquid o ...
, bobbing,
autotomy
Autotomy (from the Greek ''auto-'', "self-" and ''tome'', "severing", αὐτοτομία) or self-amputation, is the behaviour whereby an animal sheds or discards one or more of its own appendages, usually as a self-defense mechanism to elude ...
, fleeing,
stridulation
Stridulation is the act of producing sound by rubbing together certain body parts. This behavior is mostly associated with insects, but other animals are known to do this as well, such as a number of species of fish, snakes and spiders. The mech ...
,
retaliation
Revenge is committing a harmful action against a person or group in response to a grievance, be it real or perceived. Francis Bacon described revenge as a kind of "wild justice" that "does... offend the law ndputteth the law out of office." Pr ...
, and chemical secretions.
Thanatosis
Some animals respond to attacks by simulating an apparent death to avoid either detection or further attacks. Arachnids such as spiders practice this mechanism when threatened or even to avoid being eaten by female spiders after mating. Thanatosis is used as a second line of defense when detected by a potential predator and is commonly observed within the
Dyspnoi
Dyspnoi is a suborder of harvestmen, currently comprising 43 extant genera and 356 extant species, although more species are expected to be described in the future. The eight families are currently grouped into three superfamilies: the Acropsopil ...
and
Laniatores
Laniatores is the largest suborder of the arachnid order Opiliones with over 4,000 described species worldwide. The majority of the species are highly dependent on humid environments and usually correlated with tropical and temperate forest habit ...
suborders, with individuals becoming rigid with legs either retracted or stretched.Eisner, T., Alsop, D., Meinwald, J., 1978. Secretions of Opilionids, Whip Scorpions and Pseudoscorpions, in: Arthropod Venoms, Handbook of Experimental Pharmacology / Handbuch Der Experimentellen Pharmakologie. Springer, Berlin, Heidelberg, pp. 87–99.Machado, G., Pomini, A.M., 2008. Chemical and behavioral defenses of the neotropical harvestman Camarana flavipalpi (Arachnida: Opiliones). Biochem. Syst. Ecol. 36, 369–376.
Freezing
Freezing – or the complete halt of movement – has been documented in the family Sclerosomatidae. While this can mean an increased likelihood of immediate survival, it also leads to reduced food and water intake.Chelini, M.-C., Willemart, R.H., Hebets, E.A., 2009. Costs and benefits of freezing behaviour in the harvestman Eumesosoma roeweri (Arachnida, Opiliones). Behav. Processes 82, 153–159.
Bobbing
To deflect attacks and enhance escape, long-legged species – commonly known as daddy long-legs – from the
Eupnoi
The Eupnoi are a suborder of harvestmen, with more than 200 genera, and about 1,700 described species.
They consist of two superfamilies, the Phalangioidea with many long-legged species common to northern temperate regions, and the small group C ...
suborder, use two mechanisms. One is bobbing, for which these particular individuals bounce their bodies. It potentially serves to confuse and deflect any identification of the exact location of their bodies. This can be a deceiving mechanism to avoid predation when they are in a large aggregation of individuals, which are all trembling at the same time.Escalante, I., Albín, A., Aisenberg, A., 2013. Lacking sensory (rather than locomotive) legs affects locomotion but not food detection in the harvestman Holmbergiana weyenberghi. Can. J. Zool. 91, 726–731. Cellar spiders ( Pholcidae) that are commonly mistaken for daddy long-legs (Opiliones) also exhibit this behavior when their webs are disturbed or even during courtship.
Autotomy
Autotomy is the voluntary amputation of an appendage, and is employed to escape when restrained by a predator.Roth, V.D., Roth, B.M., 1984. review of appendotomy in spiders and other arachnids. Bull.-Br. Arachnol. Soc. Eupnoi individuals, more specifically sclerosomatid harvestmen, commonly use this strategy in response to being captured.Houghton, J.E., Townsend, V.R., Proud, D.N., 2011. The Ecological Significance of Leg Autotomy for Climbing Temperate Species of Harvestmen (Arachnida, Opiliones, Sclerosomatidae). Southeast. Nat. 10, 579–590.Guffey, C., 1998. Leg Autotomy and Its Potential Fitness Costs for Two Species of Harvestmen (Arachnida, Opiliones). J. Arachnol. 26, 296–302. This strategy can be costly because harvestmen do not regenerate their legs, and leg loss reduces locomotion, speed, climbing ability, sensory perception, food detection, and territoriality.
Autotomized legs provide a further defense from predators because they can twitch for 60 seconds to an hour after detachment. This can also potentially serve as deflection from an attack and deceive a predator from attacking the animal. It has been shown to be successful against ants and spiders.
The legs continue to twitch after they are detached because 'pacemakers' are located in the ends of the first long segment (femur) of their legs. These pacemakers send signals via the nerves to the muscles to extend the leg and then the leg relaxes between signals. While some harvestman's legs twitch for a minute, others have been recorded to twitch up to an hour. The twitching has been hypothesized to function as an evolutionary advantage by keeping the attention of a predator while the harvestman escapes.
Fleeing
Individuals that are able to detect potential threats can flee rapidly from attack. This is seen with multiple long-legged species in the
Leiobunum
''Leiobunum'' is a genus of the harvestman family Sclerosomatidae with more than 100 described species. Contrary to popular belief, they are not spiders, although they share a resemblance. They are arachnids, in the order Opiliones, harvestmen. ...
clade that either drop and run, or drop and remain motionless. This is also seen when disturbing an aggregation of multiple individuals, where they all scatter.
Stridulation
Multiple species within the Laniatores and Dyspnoi possess
stridulating
Stridulation is the act of producing sound by rubbing together certain body parts. This behavior is mostly associated with insects, but other animals are known to do this as well, such as a number of species of fish, snakes and spiders. The mech ...
organs, which are used as intraspecific communication and have also been shown to be used as a second line of defense when restrained by a predator.
Retaliation
Armored harvestmen in Laniatores can often use their modified morphology as weapons.Dias, B.C., Willemart, R.H., 2013. The effectiveness of post-contact defenses in a prey with no pre-contact detection. Zoology 116, 168–174.Segovia, J.M.G., Del-Claro, K., Willemart, R.H., 2015. Defences of a Neotropical harvestman against different levels of threat by the recluse spider. Behaviour 152, 757–773. Many have spines on their pedipalps, back legs, or bodies. By pinching with their chelicerae and pedipalps, they can cause harm to a potential predator. Also this has been proven to increase survival against recluse spiders by causing injury, allowing the harvestman to escape from predation.
Chemical
Harvestmen are well known for being chemically protected. They exude strongly odored secretions from their scent glands, called
ozopore
An ozopore is the opening of a defensive gland present in some arthropods, notably in millipedes of the order Polydesmida that act as a shield against predators; this is the most effective defense they use which creates a strong and unpleasant taste. In ''Cyphophthalmi'' the scent glands release naphthoquinones, chloro-naphthoquinones and aliphatic methyl ketones, ''Insidiatores'' use nitrogen-containing substances, terpenes, aliphatic ketones, and phenolics, while ''Grassatores'' use alkylated phenolics and benzoquinones, and ''Palpatores'' use substances like naphthoquinones, methyl- and ethyl-ketones, and naphthoquinones. These secretions have successfully protected the harvestmen against wandering spiders (
Ctenidae
Wandering spiders (''Ctenidae'') are a family of spiders that includes the Brazilian wandering spiders. These spiders have a distinctive longitudinal groove on the top-rear of their oval carapace similar to those of the Amaurobiidae. They are hig ...
), wolf spiders (Lycosidae) and ''Formica exsectoides'' ants. However, these chemical irritants are not able to prevent four species of harvestmen being preyed upon by the black scorpion ''
Bothriurus
''Bothriurus'' is a genus of Neotropical 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 cha ...
bonariensis'' (
Bothriuridae
The Bothriuridae are a family of 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 characteris ...
). These secretions contain multiple volatile compounds that vary among individuals and clades.
Endangered status
All
troglobitic
A troglobite (or, formally, troglobiont) is an animal species, or population of a species, strictly bound to underground habitats, such as caves. These are separate from species that mainly live in above-ground habitats but are also able to live u ...
species (of all animal taxa) are considered to be at least threatened in Brazil. Four species of Opiliones are on the Brazilian national list of endangered species, all of them cave-dwelling: '' Giupponia chagasi'', ''Iandumoema uai'', ''Pachylospeleus strinatii'' and ''Spaeleoleptes spaeleus''.
Several Opiliones in Argentina appear to be vulnerable, if not endangered. These include ''Pachyloidellus fulvigranulatus'', which is found only on top of Cerro Uritorco, the highest peak in the Sierras Chicas chain (provincia de Cordoba) and ''Pachyloides borellii'' is in rainforest patches in northwest Argentina which are in an area being dramatically destroyed by humans. The cave-living ''Picunchenops spelaeus'' is apparently endangered through human action. So far, no harvestman has been included in any kind of a Red List in Argentina, so they receive no protection.
''Maiorerus randoi'' has only been found in one cave in the Canary Islands. It is included in the Catálogo Nacional de especies amenazadas (National catalog of threatened species) from the
Spanish
Spanish might refer to:
* Items from or related to Spain:
**Spaniards are a nation and ethnic group indigenous to Spain
**Spanish language, spoken in Spain and many Latin American countries
**Spanish cuisine
Other places
* Spanish, Ontario, Can ...
government.
''
Texella reddelli
''Texella reddelli'', the Bee Creek cave harvestman, is a rare species of troglobitic harvestman that was added to the United States endangered species list in 1988, at the same time as six other species native to the karst ecosystem in Travis Co ...
'' and ''
Texella reyesi
''Texella reyesi'' is a rare species of arachnid known by the common name Bone Cave harvestman. It is endemic to Texas in the United States, where it lives in limestone caves in Travis and Williamson Counties. It is threatened by the loss of it ...
'' are listed as endangered species in the United States. Both are from caves in central Texas. '' Texella cokendolpheri'' from a cave in central Texas and ''Calicina minor'', ''Microcina edgewoodensis'', ''Microcina homi'', ''Microcina jungi'', ''Microcina leei'', ''Microcina lumi'', and ''Microcina tiburona'' from around springs and other restricted habitats of central California are being considered for listing as endangered species, but as yet receive no protection.
Misconception
An urban legend claims that the harvestman is the most venomous animal in the world but possesses fangs too short or a mouth too round and small to bite a human, rendering it harmless (the same myth applies to ''
Pholcus phalangioides
''Pholcus phalangioides'', commonly known as daddy long-legs spider or long-bodied cellar spider, is a spider of the family Pholcidae. It is also known as the skull spider, since its cephalothorax resembles a human skull. This is the only spide ...
'' and the
cranefly
Crane fly is a common name referring to any member of the insect family Tipulidae. Cylindrotominae, Limoniinae, and Pediciinae have been ranked as subfamilies of Tipulidae by most authors, though occasionally elevated to family rank. In the m ...
, which are both also called a "daddy longlegs"). This is untrue on several counts. None of the known species of harvestmen have venom glands; their
chelicerae
The chelicerae () are the mouthparts of the subphylum Chelicerata, an arthropod group that includes arachnids, horseshoe crabs, and sea spiders. Commonly referred to as " jaws", chelicerae may be shaped as either articulated fangs, or similarl ...
are not hollowed fangs but grasping claws that are typically very small and not strong enough to break human skin.
Research
Harvestmen are a scientifically neglected group. Description of new taxa has always been dependent on the activity of a few dedicated taxonomists.
Carl Friedrich Roewer
Carl Friedrich Roewer (12 October 1881, in Neustrelitz – 17 June 1963) was a German arachnologist. He concentrated on harvestmen, where he described almost a third (2,260) of today's known species, but also almost 700 taxa of spiders and numerou ...
described about a third (2,260) of today's known species from the 1910s to the 1950s, and published the landmark systematic work (Harvestmen of the World) in 1923, with descriptions of all species known to that time. Other important taxonomists in this field include:
*
Pierre Latreille
Pierre is a masculine given name. It is a French form of the name Peter. Pierre originally meant "rock" or "stone" in French (derived from the Greek word πέτρος (''petros'') meaning "stone, rock", via Latin "petra"). It is a translation ...
(18th century)
*
Carl Ludwig Koch
Carl Ludwig Koch (21 September 1778 – 23 August 1857) was a German entomologist and arachnologist. He was responsible for classifying a great number of spiders, including the Brazilian whiteknee tarantula and common house spider. He was bor ...
,
Maximilian Perty
Josef Anton Maximilian Perty (17 September 1804, Ornbau – 8 August 1884, Bern) was a German naturalist and entomologist. He was a professor of zoology and comparative anatomy at the University of Bern.L. Koch,
Tord Tamerlan Teodor Thorell
Tord Tamerlan Teodor Thorell (3 May 1830 – 22 December 1901) was a Swedish arachnologist.
Thorell studied spiders with Giacomo Doria at the Museo Civico di Storia Naturale de Genoa. He corresponded with other arachnologists, such as Octaviu ...
Cândido Firmino de Mello-Leitão
Cândido Firmino de Mello-Leitão (July 17, 1886 – December 14, 1948) was a Brazilian zoologist who is considered the founder of Arachnology in South America, publishing 198 papers on the taxonomy of Arachnida. He was also involved with edu ...
(20th century)
*
Gonzalo Giribet
Gonzalo Giribet is a Spanish-American invertebrate zoologist and Alexander Agassiz Professor of zoology working on systematics and biogeography at the Museum of Comparative Zoology in Harvard University. He is a past president of the Internationa ...
, Adriano Brilhante Kury, Tone Novak (21st century)
Since the 1990s, study of the biology and ecology of harvestmen has intensified, especially in South America.
Phylogeny
Harvestmen are ancient
arachnid
Arachnida () is a class of joint-legged invertebrate animals (arthropods), in the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, harvestmen, camel spiders, whip spiders and vinegaro ...
Rhynie chert
The Rhynie chert is a Lower Devonian sedimentary deposit exhibiting extraordinary fossil detail or completeness (a Lagerstätte). It is exposed near the village of Rhynie, Aberdeenshire, Scotland; a second unit, the Windyfield chert, is located ...
, 410 million years ago, already show characteristics like tracheae and sexual organs, indicating that the group has lived on land since that time. Despite being similar in appearance to, and often confused with, spiders, they are probably closely related to the scorpions,
pseudoscorpion
Pseudoscorpions, also known as false scorpions or book scorpions, are small, scorpion-like arachnids belonging to the order Pseudoscorpiones, also known as Pseudoscorpionida or Chelonethida.
Pseudoscorpions are generally beneficial to humans sin ...
s, and
solifuge
Solifugae is an order of animals in the class Arachnida known variously as camel spiders, wind scorpions, sun spiders, or solifuges. The order includes more than 1,000 described species in about 147 genera. Despite the common names, they are n ...
s; these four orders form the clade Dromopoda. The Opiliones have remained almost unchanged morphologically over a long period. Indeed, one species discovered in China, ''Mesobunus martensi'', fossilized by fine-grained volcanic ash around 165 million years ago, is hardly discernible from modern-day harvestmen and has been placed in the extant family
Sclerosomatidae
The Sclerosomatidae are a family of harvestmen with about 1,300 known species.
Name
The name is combined from Ancient Greek ''skleros'' "hard" and ''soma'' "body". (2007): Sclerosomatidae. Simon, 1879. In: Pinto-da-Rocha ''et al.'' 2007: 127ff
...
.
Etymology
The Swedish naturalist and arachnologist
Carl Jakob Sundevall
Carl Jakob Sundevall (22 October 1801, Högestad – 2 February 1875) was a Swedish zoologist.
Sundevall studied at Lund University, where he became a Ph.D. in 1823. After traveling to East Asia, he studied medicine, graduating as Doctor of Me ...
(1801–1875) honored the naturalist Martin Lister (1638–1712) by adopting Lister's term Opiliones for this order, known in Lister's days as "harvest spiders" or "shepherd spiders", from Latin ''opilio'', "shepherd"; Lister characterized three species from England (although not formally describing them, being a pre-Linnaean work).
In England, the Opiliones are called harvestmen, not because they appear at that season, but from a superstitious belief that if one be killed there will be a bad harvest that year.
Systematics
The interfamilial relationships within Opiliones are not yet fully resolved, although significant strides have been made in recent years to determine these relationships. The following list is a compilation of interfamilial relationships recovered from several recent phylogenetic studies, although the placement and even monophyly of several taxa are still in question.
* Suborder
Cyphophthalmi
Cyphophthalmi is a suborder of harvestmen, colloquially known as mite harvestmen. Cyphophthalmi comprises 36 genera, and more than two hundred described species. The six families are currently grouped into three infraorders: the Boreophthalmi, Sc ...
Eupnoi
The Eupnoi are a suborder of harvestmen, with more than 200 genera, and about 1,700 described species.
They consist of two superfamilies, the Phalangioidea with many long-legged species common to northern temperate regions, and the small group C ...
Phalangioidea
Phalangioidea is a superfamily of the harvestman suborder Eupnoi with five recognized families and more than 1,500 species.
It is not to be confused with the similar spelled subfamily Phalangodoidea, which is also a harvestman superfamily, but ...
Sclerosomatidae
The Sclerosomatidae are a family of harvestmen with about 1,300 known species.
Name
The name is combined from Ancient Greek ''skleros'' "hard" and ''soma'' "body". (2007): Sclerosomatidae. Simon, 1879. In: Pinto-da-Rocha ''et al.'' 2007: 127ff
...
Simon 1879
* Suborder
Dyspnoi
Dyspnoi is a suborder of harvestmen, currently comprising 43 extant genera and 356 extant species, although more species are expected to be described in the future. The eight families are currently grouped into three superfamilies: the Acropsopil ...
Ischyropsalididae
Ischyropsalididae is a family of harvestmen
The Opiliones (formerly Phalangida) are an order of arachnids colloquially known as harvestmen, harvesters, harvest spiders, or daddy longlegs. , over 6,650 species of harvestmen have been discover ...
Simon 1879
*** Family
Sabaconidae
Sabaconidae is a family of harvestmen with 57 described species in one genus, ''Sabacon'', which is found throughout the Northern Hemisphere.
Name
The name of the type genus is derived from "Sabacon", an Egyptian king.
Description
This family ...
Dresco 1970
*** Family Taracidae Schönhofer 2013
** Superfamily Troguloidea Sundevall 1833
*** Family
Dicranolasmatidae
The Dicranolasmatidae are a family of harvestmen with 16 described species in a single genus, ''Dicranolasma''.
Description
Species of ''Dicranolasma'' range in body length from three to 6.4 mm. Most parts of the body are encrusted with soi ...
Simon 1879
*** Family
Nemastomatidae
The Nemastomatidae are a family of harvestmen with about 170 described species in 16 recent genera. Several fossil species and genera are known.
Unlike some related currently recognized families, the Nemastomatidae are monophyletic. (2007): Nema ...
Simon 1872
*** Family
Nipponopsalididae
Nipponopsalididae is a family of harvestmen with three described species in one genus, ''Nipponopsalis'', which is found in East Asia.
Name
The genus name ''Nipponopsalis'' is a combination of ''Nippon'', meaning Japan, where the genus was first ...
Martens 1976
*** Family
Trogulidae
Trogulidae is a family of harvestmen with 5 genera and 57 extant species and one fossil species.
Members of this species have short legs and live in soil. They have dirt attached to their bodies, to escape predators. Their body length ranges fr ...
Sundevall 1833
* Suborder
Laniatores
Laniatores is the largest suborder of the arachnid order Opiliones with over 4,000 described species worldwide. The majority of the species are highly dependent on humid environments and usually correlated with tropical and temperate forest habit ...
Grassatores
The Grassatores are the most diverse infraorder of the Laniatores. It includes over 3,500 species distributed mainly in the tropics
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropi ...
Gonyleptidae
Gonyleptidae is a neotropical family of harvestmen (Order Opiliones) with more than 800 species, the largest in the Suborder Laniatores and the second largest of the Opiliones as a whole. The largest known harvestmen are gonyleptids.
Like most h ...
Despite their long history, few harvestman fossils are known. This is mainly due to their delicate body structure and terrestrial habitat, making them unlikely to be found in sediments. As a consequence, most known fossils have been preserved within
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 Ma ...
.
The oldest known harvestman, from the 410-million-year-old Devonian Rhynie chert, displayed almost all the characteristics of modern species, placing the origin of harvestmen in the Silurian, or even earlier. A recent molecular study of Opiliones, however, dated the origin of the order at about 473 million years ago (Mya), during the Ordovician.
No fossils of the
Cyphophthalmi
Cyphophthalmi is a suborder of harvestmen, colloquially known as mite harvestmen. Cyphophthalmi comprises 36 genera, and more than two hundred described species. The six families are currently grouped into three infraorders: the Boreophthalmi, Sc ...
or
Laniatores
Laniatores is the largest suborder of the arachnid order Opiliones with over 4,000 described species worldwide. The majority of the species are highly dependent on humid environments and usually correlated with tropical and temperate forest habit ...
much older than 50 million years are known, despite the former presenting a
basal clade
In phylogenetics, basal is the direction of the ''base'' (or root) of a rooted phylogenetic tree or cladogram. The term may be more strictly applied only to nodes adjacent to the root, or more loosely applied to nodes regarded as being close to th ...
, and the latter having probably diverged from the Dyspnoi more than 300 Mya.
Naturally, most finds are from comparatively recent times. More than 20 fossil species are known from the
Cenozoic
The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configurat ...
The 410-million-year-old ''Eophalangium sheari'' is known from two specimens, one a female, the other a male. The female bears an
ovipositor
The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typica ...
and is about long, whilst the male had a discernable penis. Whether both specimens belong to the same species is not definitely known. They have long legs,
tracheae
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 the la ...
, and no median eyes. Together with the 305-million-year-old ''Hastocularis argus'', it forms the suborder Tetrophthalmi.
''Brigantibunum listoni'' from East Kirkton near Edinburgh in Scotland is almost 340 million years old. Its placement is rather uncertain, apart from it being a harvestman.
From about 300 Mya, several finds are from the
Coal Measures
In lithostratigraphy, the coal measures are the coal-bearing part of the Upper Carboniferous System. In the United Kingdom, the Coal Measures Group consists of the Upper Coal Measures Formation, the Middle Coal Measures Formation and the Lower Coa ...
of North America and Europe. While the two described ''Nemastomoides'' species are currently grouped as Dyspnoi, they look more like Eupnoi.
''Kustarachne tenuipes'' was shown in 2004 to be a harvestman, after residing for almost one hundred years in its own arachnid order, the "Kustarachnida".
Some fossils from the Permian are possibly harvestmen, but these are not well preserved.
Early Carboniferous
Early may refer to:
History
* The beginning or oldest part of a defined historical period, as opposed to middle or late periods, e.g.:
** Early Christianity
** Early modern Europe
Places in the United States
* Early, Iowa
* Early, Texas
* Ear ...
Montceau-les-Mines
Montceau-les-Mines () is a commune in the Saône-et-Loire department in the region of Bourgogne-Franche-Comté in eastern France.
It is the second-largest commune of the metropolitan Communauté urbaine Creusot Montceau, which lies southwest o ...
Currently, no fossil harvestmen are known from 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 period ...
Crato Formation
The Crato Formation is a geologic formation of Early Cretaceous (Aptian) age in northeastern Brazil's Araripe Basin. It is an important Lagerstätte (undisturbed fossil accumulation) for palaeontologists. The strata were laid down mostly duri ...
of Brazil, a
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 ...
that has yielded many other terrestrial arachnids. An unnamed long-legged harvestman was reported from the Early Cretaceous of
Koonwarra
Koonwarra is a town in the South Gippsland region of Victoria, Australia. At the , Koonwarra had a population of 404. The town straddles the South Gippsland Highway. Located around 128 km southeast of Melbourne, the town was served by rail ...
,
Victoria
Victoria most commonly refers to:
* Victoria (Australia), a state of the Commonwealth of Australia
* Victoria, British Columbia, provincial capital of British Columbia, Canada
* Victoria (mythology), Roman goddess of Victory
* Victoria, Seyche ...
, Australia, which may be a Eupnoi.
A fossil of '' Halitherses grimaldii'', a long-legged Dyspnoi with large eyes, was found in
Burmese amber
Burmese amber, also known as Burmite or Kachin amber, is amber from the Hukawng Valley in northern Myanmar. The amber is dated to around 100 million years ago, during the latest Albian to earliest Cenomanian ages of the mid-Cretaceous period. The ...
dating from approximately 100 Mya. It has been suggested that this may be related to the Ortholasmatinae (Nemastomatidae).
Cenozoic
Unless otherwise noted, all species are from the Eocene.
* '' Troguluslongipes'' Haupt, 1956 (Dyspnoi:
Trogulidae
Trogulidae is a family of harvestmen with 5 genera and 57 extant species and one fossil species.
Members of this species have short legs and live in soil. They have dirt attached to their bodies, to escape predators. Their body length ranges fr ...
) —
Geiseltal The Geisel valley (german: Geiseltal) is a valley in Saxony-Anhalt, Germany, situated west of Merseburg, Saalekreis district. It is named after the River Geisel which rises in Mücheln and is a tributary of the Saale, just under long.
Its main ...
Caddo
The Caddo people comprise the Caddo Nation of Oklahoma, a federally recognized tribe headquartered in Binger, Oklahoma. They speak the Caddo language.
The Caddo Confederacy was a network of Indigenous peoples of the Southeastern Woodlands, who ...
Baltic amber
The Baltic region is home to the largest known deposit of amber, called Baltic amber or succinite. It was produced sometime during the Eocene epoch, but exactly when is controversial. It has been estimated that these forests created more than ...
Opilio
''Opilio'' is a genus of harvestmen with more than 60 known species.
Name
The genus name is derived from Latin ''opilio'' "sheep-master" (a kind of slave), used by Plautus, also used by Virgil with the meaning "shepherd".Pinto-da-Rocha, R., Mac ...
Leiobunum
''Leiobunum'' is a genus of the harvestman family Sclerosomatidae with more than 100 described species. Contrary to popular belief, they are not spiders, although they share a resemblance. They are arachnids, in the order Opiliones, harvestmen. ...
Sclerosomatidae
The Sclerosomatidae are a family of harvestmen with about 1,300 known species.
Name
The name is combined from Ancient Greek ''skleros'' "hard" and ''soma'' "body". (2007): Sclerosomatidae. Simon, 1879. In: Pinto-da-Rocha ''et al.'' 2007: 127ff
...
Nemastomatidae
The Nemastomatidae are a family of harvestmen with about 170 described species in 16 recent genera. Several fossil species and genera are known.
Unlike some related currently recognized families, the Nemastomatidae are monophyletic. (2007): Nema ...
Sabaconidae
Sabaconidae is a family of harvestmen with 57 described species in one genus, ''Sabacon'', which is found throughout the Northern Hemisphere.
Name
The name of the type genus is derived from "Sabacon", an Egyptian king.
Description
This family ...
Phalangioidea
Phalangioidea is a superfamily of the harvestman suborder Eupnoi with five recognized families and more than 1,500 species.
It is not to be confused with the similar spelled subfamily Phalangodoidea, which is also a harvestman superfamily, but ...
) —
Florissant Fossil Beds National Monument
The Florissant Formation is a sedimentary geologic formation outcropping around Florissant, Teller County, Colorado. The formation is noted for the abundant and exceptionally preserved insect and plant fossils that are found in the mudstones and ...