The Sydney funnel-web spider Atrax robustus, is a notoriously dangerous Australian funnel-web spider usually found within a 100 km (62 mi) radius of Sydney, New South Wales, Australia.

[edit] Description

Female Sydney funnel-web spider in warning posture

Sydney funnel-webs are medium-to-large in size, with a body length ranging from 2 cm to 7 cm (0.9" to 3"). They are glossy and darkly coloured, ranging from blue-black to black to brown or dark-plum coloured. The carapace covering the cephalothorax is almost hairless and so appears smooth and glossy. Males are smaller than females.

It is the only species in the genus Atrax, contained by the family Hexathelidae.^[1] The common name of the species is shared by others, members of the genus Hadronyche, but it and the northern tree funnel-web are the only Australian funnel-web spiders known to have inflicted fatal bites to humans.

[edit] Behaviour

The spider can be very aggressive when provoked. The long-lived female funnel-webs spend most of the time in their silk-lined tubular burrow retreats. Males, recognized by the modified terminal segment of the palp, tend to wander during the warmer months of the year looking for receptive females of their kind for mating.^[2] They are attracted to water and hence are often found in swimming pools where they have fallen while wandering. The spiders can survive such immersion for up to twenty-four hours and can deliver a bite when removed from the water.

They are mostly terrestrial spiders, favouring habitat with moist sand and clays. They typically build silk-lined tubular burrow retreats with collapsed "tunnels" or open "funnel" entrances from which irregular trip lines radiate out over the ground. In some exceptions, which lack trip lines but may have trapdoors, the silk entrance tube may be split into two openings, in a Y or T form. The burrow may be in the hollow of a tree trunk or limb, many metres above ground level.

[edit] Distribution

Distribution is primarily South of the Hunter River to the Illawarra region, and west to the Blue Mountains in New South Wales. However, the Sydney funnel-web spider has been found as far away as Canberra, 250 km from Sydney.

[edit] Venom

Funnel-web spider venom contains a compound known as atraxotoxin which is highly toxic to primates. These spiders typically deliver a full envenomation when they bite, due to their aggressiveness and large chitinous cheliceral fangs. For this reason, humans are strongly advised not to approach them. Chances of being bitten are high if encountered. There is at least one recorded case of a small child dying within 15 minutes of a bite from a Sydney funnel-web spider; that event occurred before the development of an antivenom. For very small children the amount of venom dispersed throughout the body is many times the concentration in an adult. Since the antivenom was developed in 1981^[3], there have been no recorded fatalities due to this species.

[edit] References