The Sydney funnel-web spider (Atrax robustus) is a species of venomous mygalomorph spider native to eastern Australia, usually found within a 100 km (62 mi) radius of Sydney. It is a member of a group of spiders known as Australian funnel-web spiders. Its bite is capable of causing serious illness or death in humans if left untreated.
The Sydney funnel-web has a body length ranging from 1 to 5 cm (0.4 to 2 in). Both sexes are glossy and darkly coloured, ranging from blue-black, to black, to brown or dark-plum coloured.
They typically build silk-lined tubular burrow retreats with collapsed "tunnels" or open "funnel" entrances from which irregular trip-lines radiate 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 spiders burrow in sheltered habitats where they can find a moist and humid climate; for instance under rocks, logs or borer holes in rough-barked trees.
The lethal dose of venom in humans is not known. The lethal dose of venom from male Sydney funnel-web spiders for the crab-eating macaque (Macaca fascicularis) is 0.2 milligrams per kilogram (3.2×10 - 6 oz/lb). Higher figures were found for other experimental animals, such as 1.5 milligrams per kilogram (2.4×10 - 5 oz/lb) for two-day-old mice. The average venom yield for a male is 176 milligrams (2.72 gr).
The bite of a Sydney funnel-web is initially very painful, with clear fang marks separated by several millimetres. The size of fangs is responsible for the initial pain. In some cases the spider will remain attached until dislodged by shaking or flicking it off. Physical symptoms can include copious secretion of saliva, muscular twitching and breathing difficulty, disorientation and confusion, leading to unconsciousness.
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