|male specimen on display in the Australian Museum|
|female specimen on display in the Australian Museum|
Atrax formidabilis Rainbow
Hadronyche formidabilis, the northern tree funnel-web spider, is a highly venomous mygalomorph spider found in Queensland and New South Wales. It is also known as the Northern Rivers funnel-web spider or northern funnelweb spider.
A member of the genus Hadronyche, the northern funnelweb was first described in 1914, by William Joseph Rainbow in the genus Atrax, having been collected from the vicinity of the Richmond River. Rainbow suspected it may need to be placed in a genus separate to Atrax at the time, but demurred due to lack of male specimens. The species name is derived from the Latin formidabilis "terrifying". Within the genus Hadronyche, it is classified in the heterogeneous cerberea group, alongside the southern tree funnel-web (H. cerberea), the Blue Mountains funnel-web (H. versuta) and twelve other species from southern New South Wales and Victoria.
The northern tree funnel-web has a glossy black carapace, and matte black or dark brown chelicerae, legs and abdomen. The dorsolateral surface of the abdomen may have a plum- or purplish tinge. The carapace of both sexes is longer and thinner than other members of the genus Hadronyche. It is between 40-50 millimetres long, the largest member of the funnelweb subfamily Atracinae. The species is very similar to the ground dwelling Darling Downs funnel web (Hadronyche infensa), the male northern tree funnel-web distinguished by its knobby spur on the tibia of the second pair of legs, which the male Darling Downs funnel-web lacks. Trapdoor spiders are more brown overall in colour.
Male and female northern tree funnel-webs rear up and display their fangs when confronted, drops of venom appearing on the ends of their fangs. They are unable to jump. The venom of the species is potentially deadly to humans, and regarded as the most toxic of those in the family Hexathelidae. A high proportion of bites—five out of eight recorded cases—from the northern tree funnel-web spider result in severe symptoms of envenomation. The venom can be successfully treated with the antivenom for the related Sydney funnel-web (Atrax robustus).
Symptoms of envenomation can occur within 15 to 20 minutes. Applying pressure and a tourniquet can significantly delay the onset of symptoms and remains a critical part of management of a spider bite. Despite the venom lacking the atracotoxin or atraxin of A. robustus, the symptoms are very similar to those from a Sydney funnel-web bite. Common symptoms include diaphoresis, hypertension, sinus tachycardia, muscle spasm or fasciculation, nausea and vomiting, altered consciousness and local pain at the bite site. Pulmonary oedema occurs frequently and comes on early. As these spiders are larger than the Sydney funnel-web, it may be that they inject greater amounts of venom and are the deadliest spiders in the world.
Distribution and habitat
The northern funnel-web is found in eastern Australia from South East Queensland to the Hunter River in New South Wales. This and the southern tree funnel-web (Hadronyche cerberea) are the only two species of funnel-web that live predominantly in trees. It lives in rotting logs, branches and hollow furrows and pipes of trees, particularly tallowwood (Eucalyptus microcorys), as well as in epiphytes. They have been recorded in trees 30 m (100 ft) above the ground. Roving males are encountered after rain and at night between late October and early February. They seek shelter during the day.
The arboreal habitat suggests that wood-boring beetles are a main prey item of the northern tree funnel-web.
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