The Sydney funnel-web spider is small enough to hide in a shoe, can survive a full day at the bottom of a swimming pool, and when cornered rears up to strike downward with fangs strong enough to pierce a fingernail. Found almost entirely within 100 kilometers of Sydney, it is one of the most dangerous spiders alive, though only by accident. Its venom evolved to subdue beetles, cockroaches, and other small prey, yet the active compound happens to fit the nervous system of primates, jamming nerve channels open and sending the body into overdrive.

This episode covers the science and the strange human story around it. For decades males and females were classified as separate species, a confusion resolved only after a boy’s death in 1927 prompted a museum review. The wandering males carry the lethal venom, and symptoms can become severe in a median of 28 minutes. Then came an antivenom in 1981, and with it a remarkable arrangement in which ordinary residents catch live spiders in jars so their venom can be milked.

• Octavius Pickard-Cambridge described the species from a female in 1877, and in 1914 William Joseph Rainbow mistook the long-legged males for a new species.
• Dense hairs on the abdomen trap air bubbles, letting a spider that falls into a pool breathe underwater for up to 24 hours and walk away once scooped out.
• The venom is highly toxic to humans and monkeys but does not cause the same nervous system failure in dogs or cats.
• Since Struan Sutherland’s team developed the antivenom there have been zero recorded deaths, though a 10-year-old boy bitten in 2017 needed a record 12 vials.
• It takes roughly 70 milkings to make a single dose, so the Australian Reptile Park asks the public to deliver live spiders to drop-off points.