Wandering and mating

After they mature, male spiders leave their burrows and become wanderers, especially during the summer/autumn months, looking for females in their burrows. Chemicals called pheromones in the female's tripline silk help the male locate and identify her burrow. Well before mating, the male spins a small silk sperm web, onto which he deposits a droplet of sperm from his abdominal genital pore. The sperm it is then taken up and stored in the mating organs at the ends of the male's palps.

The spur and/or spines on the male's second legs are used to hold the female during mating. During mating, considerable sparring occurs until the female accepts the male. Both spiders rear up with first legs raised against each other, while the male engages his mating spurs across the bases of the female's second legs. The male then inseminates the female by inserting the tips of his palpal organs into the female's genital opening on the underside of her abdomen.

The male factor

Only male spiders have been responsible for all recorded funnel-web envenomation deaths - why is it so? The answer lies in a combination of spider behaviour, venom chemistry, and even colonial politics.

During the warmer months of the year (November-April) male funnel-webs wander about at night looking for females in their burrows. Males wandering in suburban gardens may sometimes become trapped inside houses or garages, especially those with concrete slab foundations where entry points under doors are easily reached.

The venom of the male Sydney Funnel-web Spider is very toxic. This is because male spider venom contains a unique component called Robustoxin (d-Atracotoxin-Ar1) that severely and similarly affects the nervous systems of humans and monkeys, but not of other mammals. The absence of this chemical from female Sydney Funnel-web Spider venom explains why bites by these females have not caused any deaths. However, not all funnel-web species show such a large gender-based difference in venom toxicity. Almost four million people live in the Sydney region, the centre of the distribution of the Sydney Funnel-web Spider. This makes the likelihood of human encounters with this spider much greater than in less urbanised areas like the Blue Mountains. This situation, of course, stems from a political decision made in London more than 220 years ago, to establish a colony in 'New South Wales' at Sydney Cove, a site nominated by Captain James Cook after his voyage of exploration.

Taken together, these ingredients produce a recipe for unexpected and potentially life-threatening encounters.

Funnel-web Spider antivenom

An antivenom for the Sydney Funnel-web Spider was first developed for clinical use in 1981 by Dr Struan Sutherland and his team at the Commonwealth Serum Laboratories. No deaths have occurred since its introduction. At the same time Sutherland experimentally established the effectiveness of the compression/immobilisation first aid technique for funnel-web bite. Much of the venom for this research was supplied through a funnel-web venom milking program at the Australian Reptile Park. This antivenom has also been effective against other dangerous funnel-web spider species. As well, it has been successfully used in cases of mouse spider envenomation. Antivenom is held at major city and regional hospitals.

Other dangerous funnel-web species

All suspected bites by any funnel-web spider should be regarded as potentially dangerous and treated accordingly. Besides Atrax robustus several other species have been sporadically involved in life threatening envenomations. They include the Blue Mountains Funnel-web Spider (Hadronyche versuta) and the Southern and Northern Tree Funnel-web Spiders (H. cerberea and H. formidabilis).

First aid for Funnel-web Spider bites - why and how

Despite the availability of an effective antivenom, correct and immediate first aid is still an essential requirement for funnel-web spider (and mouse spider) envenomation. The recommended first aid technique is pressure/immobilisation (as for snake bite) and this must be done as quickly as possible.The pressure/immobilisation technique compresses surface tissues and reduces muscle movement, greatly slowing the lymphatic flow.

Spider bites usually take place on a limb. A pressure bandage should be applied as soon as possible after a bite has occurred. This should be applied as tightly as for a sprained ankle, starting from the bitten area and binding the entire limb above the bite. A rigid splint should be bound onto the limb to prevent limb movement. The patient should be kept as quiet as possible and medical attention sought. If possible, keep the spider for positive identification.