The Natural History of Tarantula Spiders Essays

Submitted By supersmooth09
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The Natural History of Tarantula Spiders
Richard C. Gallon
In this article I have attempted to present a varied, fresh account of what a tarantula is and what it does. This article although laden with jargon will hopefully provide snippets of interesting information for those interested in tarantulas (theraphosids). I have divided the article into sections so that readers can easily refer to areas of specific interest.
Taxonomic Position
Tarantulas are a group of around 820 species of large, generally hairy, spiders.

All tarantulas belong to the Theraphosidae family, which resides in the Mygalomorphae infraorder. Like the mygalomorphs, araneomorphs (true spiders) are also included in the spider suborder Opisthothelae. They are however easily differentiated from the araneomorphs (true spiders) by the articulation of their chelicerae or jaws. In mygalomorphs the jaws are positioned in such a way that they strike downwards towards the ground whereas araneomorph jaws close together in a sideways pincer movement. The second suborder of spiders (Mesothelae) has mygalomorph type jaws, but uniquely possess an abdomen covered dorsally with ‘armour’ plates.
The theraphosids share the mygalomorph infraorder with 14 other spider families. They differ from these other families in a number of ways, but no single feature can used to distinguish them. Typically tarantulas possess thick scopulae (pads of specialised hair) on the undersides of their metatarsi and tarsi. Their tarsi also have claw tufts, which as their name suggests, are tufts of scopulae located next to their tarsal claws. The vast majority of tarantulas have long finger-like end segments to their posterior spinnerets. An additional differentiating feature is the possession of a prominent anterior lobe on the maxilla. This feature is useful in separating the Theraphosidae from the very similar Barychelidae, which have a weak anterior lobe.
The Theraphosidae family is further subdivided into 13 subfamilies. The actual number of subfamilies varies depending on which taxonomist you talk to. This is because not all agree on the validity of some of the taxa.
Of the New World subfamilies the largest by far is the Theraphosinae. This includes the majority of terrestrial species found in the Americas (e.g. Grammostola, Aphonopelma, Theraphosa and Brachypelma). The Aviculariinae subfamily comes second with three of the four genera being arboreal in nature. This subfamily houses the genera Avicularia, Ephebopus, Pachistopelma and Tapinauchenius. Some taxonomists feel that Psalmopoeus should also be included in this subfamily, but the evidence for this is weak to say the least. Most taxonomists believe that Psalmopoeus belongs to the Selenocosmiinae subfamily. The cave dwelling members of the genus Spelopelma are given their own subfamily (Spelopelminae). Likewise the genus Acanthopelma is also in a monogeneric subfamily (Acanthopelminae). Four of the New World genera are referable to a temporary group termed ‘New World Ischnocolinae’. These are not closely related to the Old World Ischnocolinae.
Africa is the exclusive home of the Eumenophorinae, Stromatopelminae and Harpactirinae subfamilies. The most familiar members of the Eumenophorinae are the Hysterocrates spp. and Citharischius crawshayi. Popular captive genera of the Harpactirinae include Pterinochilus and Ceratogyrus. Members of the Ischnocolinae and Selenogyrinae subfamilies are also represented in the African theraphosid fauna.
Asia also plays host to its fair share of endemic subfamilies (Ornithoctoninae, Thrigmopoeinae and Poecilotheriinae). Although one genera from the Selenocosmiinae exists in the New World, the primary home of this subfamily is South East Asia. Theraphosids from the Selenogyrinae and Ischnocolinae taxa are also found in the Asiatic region.
The only subfamily found in Australia is Selenocosmiinae. Like Australia, mainland Europe also has an impoverished tarantula fauna. Its…