October 30, 2026 — 5:12pm

Every Halloween, we invite monsters into our homes. Vampires, zombies, murderous clowns – all reassuringly imaginary. I find it harder to be frightened by them these days. I spend too much of my working life contemplating creatures whose real-life talents would be rejected by a horror screenwriter as excessive.

An enormous “murder” hornet whose sting has been compared with having a hot nail driven into your flesh. An alga called “rock snot” that can smother riverbeds in great mats of slime. Or how about a beetle the size of a sesame seed that carries a fungus capable of killing magnificent old trees. Welcome to my nightmares.

Ugly by name, ugly by nature: Rock snot is an unwelcome addition to most environments. Teresa Trimm

Having spent decades working on invasive species and extinction, I am frequently asked which potential invaders worry me most. It is a surprisingly difficult question.…