''Atrax'' is 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 ...

of venomous Australian funnel web spiders that was first described by O. Pickard-Cambridge in 1877 from the type species ''

Atrax robustus The Sydney funnel-web spider (''Atrax robustus'') is a species of venomous mygalomorph spider native to eastern Australia, usually found within a radius of Sydney. It is a member of a group of spiders known as Australian funnel-web spiders. ...

''. it contains only three species: ''A. robustus'', '' A. sutherlandi'', and '' A. yorkmainorum''. Originally placed with the curtain web spiders, it was moved to the

Hexathelidae Hexathelidae is a family of mygalomorph spiders. It is one of a number of families and genera of spiders known as funnel-web spiders. In 2018, the family was substantially reduced in size by genera being moved to three separate families: Atracid ...

in 1980, then to the Australian funnel-web spiders in 2018.

Description

They are medium to large

spiders 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 di ...

for their family ranging from 1.5 to 4.5 cm. As most in the

Mygalomorphae The Mygalomorphae, or mygalomorphs, are an infraorder of spiders, and comprise one of three major groups of living spiders with over 3000 species, found on all continents except Antarctica. Many members are known as trapdoor spiders due to the ...

Infraorder, they have robust bodies. With a glossy dark coloration in their carapace and legs, and a grey

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 ...

. They also have the same long life, ranging from 4 to 20 years. They are usually found in burrows with little silk lining, found under rocks or logs. With their aptly named funnel like webs. They are found in the coasts and highlands of southeastern Australia.

Identification

They can be identified from others of the same family by the large coniform apophysis on the male

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 connects ...

. And from the Hadronyche by the lower caput height. Caput being the front part of the cephalothorax.

Venom

This genus includes some of the most dangerous spiders, namely the

Sydney funnel-web spider The Sydney funnel-web spider (''Atrax robustus'') is a species of venomous mygalomorph spider native to eastern Australia, usually found within a radius of Sydney. It is a member of a group of spiders known as Australian funnel-web spiders. I ...

(''Atrax robustus).'' This spider being thought to have killed 13 people, though none have died since the anti venom has been introduced. Though still many consider this spider to be quite dangerous, and deadly. Most of the bites are thought to be caused by male spiders which wander out of their hides to find a mate.

Hides

These

usually make their burrows under rocks or logs, usually in cool humid areas. These spiders as most funnel webs aptly make funnel shaped webs. These webs have silk trip lines which radiate from the entrance. These lines function as a warning system, which tell the spiders if there is a insect or possible mate coming. Their hides might flood, forcing them to leave their hides. Although they can last a few hours in water, as they are able to trap air bubbles in their abdomen, using their hairs. They may also leave their burrow to find a mate.

Phylogeography

Phylogeography Phylogeography is the study of the historical processes that may be responsible for the past to present geographic distributions of genealogical lineages. This is accomplished by considering the geographic distribution of individuals in light of ge ...

can be understood as the historical changes or occurrences that bring about a change to a specific species or organism. After extensive studies, researches have found that there are many geographical and genetic differences that have occurred due to micro-habitat distributions. The assumption has been made that the species of ''Atrax'' have experienced a shift in genetic structure due to the niches that they inhabit. Habitats are not the only factor to this divergence; researchers have also noted the climatic events, prey availability, and natural occurrence of biodiversity.

References

External links

{{Taxonbar, from=Q15978607 Atracidae Mygalomorphae genera Spiders of Australia