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Spiders
Spiders (order Araneae) are air-breathing arthropods that have eight limbs, 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 diversity among all orders of organisms. Spiders are found worldwide on every continent except Antarctica, and have become established in nearly every land habitat. , 53,034 spider species in 136 families have been recorded by taxonomists. 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 or prosoma, and the opisthosoma, 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spider Taxonomy
Spider taxonomy is the part of taxonomy that is concerned with the science of naming, defining and classifying all spiders, members of the Araneae order of the arthropod class Arachnida, which has more than 52,700 described species. However, there are likely many species that have escaped the human eye as well as specimens stored in collections waiting to be described and classified. It is estimated that only one-third to one half of the total number of existing species have been described. Arachnologists divide spiders into two suborders with about 136 families . Due to constant research, with new species being discovered every month and others being recognized as synonyms, the number of species in the families is bound to change and only reflects the present state of knowledge. Nevertheless, the species numbers given here are useful as a guideline – see the table of families at the end of the article. History Spider taxonomy can be traced to the work of Swedish natural ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Araneomorphae
The Araneomorphae (also called the Labidognatha or "true spiders") are an infraorder of spiders. They are distinguishable by chelicerae (fangs) that point diagonally forward and cross in a pinching action, in contrast to the Mygalomorphae (tarantulas and their close kin), where they point straight down. Araneomorphs comprise the vast majority (about 93%) of living spiders. Distinguishing characteristics Most spider species are Araneomorphae, which have chelicerae, fangs that face towards each other, increasing the orientations that they can employ during prey-capture. They have fewer book lungs (when present) – usually one pair – and the females typically live one year. The Mygalomorphae have chelicerae, fangs that face towards the ground, and which are parallel to the long axis of the spider's body, thus they have only one orientation they can employ during prey capture. They have two pairs of book lungs, and the females often live many years. Image:Cheiracanthium pun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mygalomorphae
The Mygalomorphae, or mygalomorphs, are an infraorder of spiders, and comprise one of three major groups of living spiders with over 3,000 species, found on all continents except Antarctica. Many members are known as trapdoor spiders due to their creation of trapdoors over their burrows. Other prominent groups include Australian funnel web spiders and tarantulas, with the latter accounting for around one third of all mygalomorphs. Description This group of spiders comprises mostly heavy-bodied, stout-legged spiders including tarantulas, Australian funnel-web spiders, mouse spiders, and various families of spiders commonly called trapdoor spiders. Like the " primitive" suborder of spiders Mesothelae, they have two pairs of book lungs, and downward-pointing chelicerae. Because of this, the two groups were once believed to be closely related. Later it was realised that the common ancestors of all spiders had these features (a state known as symplesiomorphy). Following the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arachnid
Arachnids are arthropods in the Class (biology), class Arachnida () of the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, opiliones, harvestmen, Solifugae, camel spiders, Amblypygi, whip spiders and Uropygi, vinegaroons. Adult arachnids have eight Arthropod leg, legs attached to the cephalothorax. In some species the frontmost pair of legs has converted to a sensory function, while in others, different appendages can grow large enough to take on the appearance of extra pairs of legs. Almost all Extant taxon, extant arachnids are terrestrial animal, terrestrial, living mainly on land. However, some inhabit freshwater environments and, with the exception of the pelagic zone, marine environments as well. They comprise over 110,000 named species, of which 51,000 are species of spiders. The term is derived from the Ancient Greek, Greek word (''aráchnē'', 'spider'), from the myth of the hubristic human weaver Arachne, w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spider Silk
Spider silk is a protein fibre or silk spun by spiders. Spiders use silk to make webs or other structures that function as adhesive traps to catch prey, to entangle and restrain prey before biting, to transmit tactile information, or as nests or cocoons to protect their offspring. They can use the silk to suspend themselves from height, to float through the air, or to glide away from predators. Most spiders vary the thickness and adhesiveness of their silk according to its use. In some cases, spiders may use silk as a food source. While methods have been developed to collect silk from a spider by force, gathering silk from many spiders is more difficult than from silk-spinning organisms such as silkworms. All spiders produce silk, although some spiders do not make webs. Silk is tied to courtship and mating. Silk produced by females provides a transmission channel for male vibratory courtship signals, while webs and draglines provide a substrate for female sex pheromone ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesothelae
The Mesothelae are a suborder of spiders (order Araneae). , two extant families were accepted by the World Spider Catalog, Liphistiidae and Heptathelidae. Alternatively, the Heptathelidae can be treated as a subfamily of a more broadly circumscribed Liphistiidae. There are also a number of extinct families. This suborder is thought to form the sister group to all other living spiders, and to retain ancestral characters, such as a segmented abdomen with spinnerets in the middle and two pairs of book lungs. Extant members of the Mesothelae are medium to large spiders with eight eyes grouped on a tubercle. They are found only in China, Japan, and southeast Asia. The oldest known Mesothelae spiders are from the Carboniferous, over 300 million years ago. Taxonomy Reginald Innes Pocock in 1892 was the first to realize that the exceptional characters of the genus '' Liphistius'' (the only member of the group then known) meant that it was more different from the remaining spiders th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 parts (tagma (biology), tagmata), located towards the Posterior (anatomy), posterior end; see also Abdomen#Other animals, Abdomen § Other animals * Accessory claw: Modified at the tip of the in web-building spiders; used with to grip strands of the web * Anal tubercle: A small protuberance (tubercule) above the through which the anus opens * Apodeme: see * Apophysis (plural apophyses): An outgrowth or process changing the general shape of a body part, particularly the appendages; often used in describing the male : see * Atrium (plural atria): An internal chamber at the entrance to the in female Haplogynae, haplogyne spiders B * Bidentate: Having two * Book lungs: Respiratory organs on the ventral side (underside) of the , in f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chelicerae
The chelicerae () are the arthropod mouthparts, 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 as a type of pincer_(biology), pincers. Some chelicerae, such as those found on nearly all spiders, are hollow and contain (or are connected to) venom glands, used to inject venom into prey or a perceived threat. Both pseudoscorpions and Opiliones , harvestmen have additional structures on their chelicerae that are used for grooming (papillae in pseudoscorpions, cheliceral teeth in Opiliones). In ''Paratrechalea'', males and females have shown to have a chelicerae dimorphism, because the chelicerae is used as a mating signal for females. Types Chelicerae can be divided into three kinds: jackknife chelicerae, scissor chelicerae, and three-segmented wikt:chelate, chelate chelicerae. Jackknife chelicerae The jackknife chelicer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Opisthothelae
Opisthothelae is a suborder of spiders within the order Araneae, containing Mygalomorphae and Araneomorphae, but excluding Mesothelae. The Opisthothelae are sometimes presented as an unranked clade and sometimes as a suborder of Araneae. In the latter case, Mygalomorphae and Araneomorphae are treated as infraorders. The creation of this taxon has been justified by the need to distinguish these spiders from the Mesothelae, which display more primitive characteristics. The characteristics that distinguish between the Mesothelae and Opisthothelae are: * Mesothelae have a segmented abdomen with tergite plates, whereas Opisthothelae have fused abdominal segments and lack tergite plates. * The almost total absence of ganglia in the abdomen of Opisthothelae. * The almost median position of the spinnerets in the Mesothelae compared with the hindmost position of those of the Opistothelae. Description Containing all extant species of spider, except for the more primitive Mesothelae, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arthropod
Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metamerism (biology), metameric) Segmentation (biology), segments, and paired jointed appendages. In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one. They form an extremely diverse group of up to ten million species. Haemolymph is the analogue of blood for most arthropods. An arthropod has an open circulatory system, with a body cavity called a haemocoel through which haemolymph circulates to the interior Organ (anatomy), organs. Like their exteriors, the internal organs of arthropods are generally built of repeated segments. They have ladder-like nervous systems, with paired Anatomical terms of location#Dorsal and ventral, ventral Ventral nerve cord, nerve cord ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spinnerets
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 typically segmented. While most spiders have six spinnerets, some have two, four, or eight. They can move both independently and in concert. Most spinnerets are not simple structures with a single orifice producing a single thread, but complex structures of many microscopic spigots, each producing one filament. This produces the necessary orientation of the protein molecules, without which the silk would be weak and useless. Spigots can be singular or found in groups, which also permits spiders to combine multiple filaments in different ways to produce many kinds of silk for various purposes. Spinneret morphology can help arachnologists identify the taxon of a specimen and the specific morphology of a spigot can determine its use as wel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 ''cephalothorax'' and ''abdomen'' in some groups. The terms ''prosoma'' and ''opisthosoma'' may be preferred by some researchers in cases such as arachnids, where there is neither fossil nor embryonic evidence animals in this class have ever had separate heads and thoraxes, and where the ''opisthosoma'' contains organs atypical of a true ''abdomen'', such as a heart and respiratory organs.) The word ''cephalothorax'' is derived from the Greek words for head (, ') and thorax (, '). This fusion of the head and thorax is seen in chelicerates and crustaceans; in other groups, such as the Hexapoda (including insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
