Invertebrates
Sydney Funnel-Web Spider
Atrax robustus · also called funnel-web, Sydney funnel-web
The Sydney funnel-web is a glossy black, heavy-bodied spider from the forests and suburbs of one Australian city, and it has a fearsome reputation: its venom can kill a person within an hour. It also has a quieter distinction — thanks to an antivenom developed in 1981, it has not killed anyone since.
Overview
Sydney funnel-webs live within roughly 150 kilometres of Sydney, in moist, sheltered ground — under rocks and logs in forest, and in the well-drained soil of gardens, rockeries, and house foundations. The female digs a silk-lined burrow with trip-lines radiating from the entrance and a distinctive funnel or Y-shaped opening, and spends her whole life there, rushing out to grab prey that touches the lines. Males abandon their burrows on humid nights in the warm months to search for females, which is when almost all bites happen.
The venom
Funnel-web venom’s dangerous component is delta-hexatoxin, which jams the sodium channels of nerve cells, causing them to fire continuously. In a severe human envenomation this produces sweating, drooling, muscle twitching, a racing heart, dangerously high blood pressure, and fluid on the lungs, potentially leading to collapse. Children are most at risk. The venom evolved to subdue insects and deter predators; the fact that it is so potent in primates specifically — while leaving dogs and cats largely unaffected — is an evolutionary accident.
The male, the burrow, and the shoe
Nearly every serious bite is from a wandering male, six times more toxic than the female, encountered on the ground, in a garage, at the bottom of a pool, or inside a garment or boot left outside. Funnel-webs are also unusually aggressive when cornered — they rear up, showing their fangs, and can strike repeatedly, and their fangs are strong enough to pierce a fingernail or soft shoe.
From 13 deaths to none
Between the 1920s and 1980, 13 deaths were attributed to the Sydney funnel-web. In 1981 an antivenom was introduced, and every case treated with it has been reversed, including severe ones. The antivenom is produced from venom “milked” from thousands of spiders donated to the Australian Reptile Park by the public, and the programme depends on people safely catching wandering males and handing them in.
Reproduction and status
A female funnel-web lays an egg sac of around 100 eggs in her burrow and guards the spiderlings for a few months. Females can live 10 to 20 years; males die within months of their final moult. The species is Least Concern and common in its small range, and habitat loss around Sydney has less impact on it than on many spiders because it tolerates suburban conditions well.
Sydney Funnel-Web Spider: common questions
Is the Sydney funnel-web really the world's most dangerous spider?
It is frequently given that title, and its venom is genuinely among the fastest and most dangerous to humans. But the claim needs context — bites are uncommon, they are concentrated in one region, and since antivenom became available in 1981 there have been no deaths at all. Before that, 13 deaths were recorded over about 50 years. So while the potential severity is real, the actual risk to a person in Sydney today is very low.
Why is the male funnel-web so much more dangerous than the female?
The male's venom contains a higher concentration of the key toxin, delta-hexatoxin, and is estimated to be around six times more toxic to humans. Males also leave their burrows in the warmer months to search for mates, wandering across the ground, into gardens, sheds, swimming pools, and shoes left outside, which is exactly when and where people encounter them. Females stay in their burrows their whole lives and rarely bite anyone.
Why does the venom affect humans so badly when it evolved for insects?
This is one of the odd facts about funnel-web venom. Delta-hexatoxin targets sodium channels in nerve cells, and it happens that the version of that channel in primates — including humans — is unusually vulnerable to it, far more so than in the dogs, cats, and other mammals that shrug off funnel-web bites. The toxin did not evolve to harm us; humans are essentially collateral damage of a compound aimed at the spider's insect prey and its own predators.
What should you do if bitten by a funnel-web?
Treat it as a medical emergency. Apply a pressure-immobilisation bandage — firm wrapping over the bite and up the whole limb, plus a splint — to slow the venom's spread through the lymphatic system, keep the person still and calm, and get to a hospital fast. Australian hospitals in the region stock the antivenom, which is highly effective and has reversed even severe cases. Do not wash the bite (venom on the skin can help identify the spider) or apply a tourniquet.