The Caterpillar With Weaponized Bad Breath

by M.Admin | Jan 23, 2014

Soap: “What was that? Armed? What do you mean, armed? Armed with what?”
Eddie: “Er, bad breath, colourful language, feather duster . . . what do you think they’re gonna be armed with? Guns, you tit!” —Lock, Stock and Two Smoking Barrels (1998)

In A Nutshell

You might smoke four packs a day, but your nicotine tolerance pales in comparison to the hornworm caterpillar’s. This guy spends his days eating tobacco leaves, but it’s not because he likes the taste. Thanks to a special gene, the hornworm caterpillar uses the nicotine in tobacco plants to ward off hungry spiders. They actually smell so badly that spiders detect them as toxic and potentially harmful.

The Whole Bushel

Around the world, cigarettes and tobacco-related products are covered in dire health warnings. Some are pretty straightforward like, “Cigarettes can cause cancer.” Others are a little gorier, displaying horrifying pictures of tracheotomies and rotting teeth. But if the hornworm caterpillar could read, he’d just shake his head and laugh. These little larvae can handle more nicotine than Don Draper and the Cigarette Smoking Man combined. In fact, the hornworm caterpillar has a nicotine tolerance that’s 750 times greater than any measly human’s, and that comes in handy when he’s attacked by eight-legged predators.

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Wolf spiders love munching on juicy little caterpillars, but the hornworm is more of a challenge than most insects thanks to its unique diet and genetic makeup. Scientists from the Max Planck Institute of Chemical Ecology in Germany discovered these little guys occasionally chow down on tobacco plants. It’s not that they’re particularly fond of the taste, and in fact, detoxifying all that nicotine takes a really long time and really slows the caterpillar down. But as researchers found out, the hornworm has an amazing way of turning the poison into a toxic weapon, a kind of “defense halitosis.”

Hornworms use a sci-fi sounding gene called “CYP6B46” to mix the nicotine with the caterpillar’s hemolymph (essentially insect blood). When the wolf spider shows up looking for a snack, the caterpillar excretes its hemolymph through little holes known as spiracles. The spider gets a whiff of all that nicotine and decides the hornworm is way too toxic to eat. The eight-eyed arachnid takes off, and the hornworm lives to see another day. Talk about smoker’s breath.