Caterpillars Repel Spiders With Nicotine Breath

By Joelle Renstrom | 7 years ago

sm_closish-up-13-14848-large4Nature comes up with the best solutions to life’s little problems, doesn’t it? And this story is further proof of that. Caterpillars are rightfully scared of spiders, but they have a much better way of dealing with it than I do. I’ve been known to throw heavy objects across the room when I spy an eight-legged intruder, or to try and douse it with toxic chemicals. More often than not, I just leave the spider clearing to someone much braver than I. The tobacco hornworm caterpillar, however, has a better strategy. They like to munch on tobacco plants, and it turns out that they have a gene that enables them to slide that nicotine in their bellies up to their breath. You know, the way garlic and Indian food do. Just as those smells might repel someone of the opposite sex, they also repel wolf spiders, that prey on tobacco hornworm caterpillars.

The genius of this system can’t be overstated. Nicotine breath is nasty. I learned this by having a mother who smokes. My brother and I used to hide her cigarettes and incur her wrath, but we did it out of love. And because she smelled terrible when she smoked—hands, hair, breath, everything. Now I have to wonder whether she was trying to keep the spiders away, or even whether she was trying to get some time to herself. Either way, this is the first time I’ve found myself having something in common with a spider.

A team of chemical ecologists from Germany’s Max Planck Institute for Chemical Ecology published a study in Proceedings of the National Academy of Sciences, noting that this was the “first example of using bad breath as a defense.” The team performed a study in which insects ate two kinds of tobacco plants—normal ones full of nicotine, and genetically modified ones that contained no none. They then did the unthinkable—they put these poor caterpillars in container with wolf spiders. I think I would just spontaneously die if this happened to me. The spiders attacked, and the poor caterpillars who ate the genetically modified plants. But the caterpillars that ate the nicotine-producing plants sent those spiders running for the hills.

The experiment confirmed findings from an outdoor study where scientists put nicotine-free plants alongside the normal ones and let the caterpillars take their pick. The ones that ate the modified plants tended to disappear overnight thanks to hungry spiders. Entomologists believe that studying insects in the wild is the key to making such discoveries. The halitosis defense “would never have been uncovered in just the lab,” says University of Illinois at Urbana-Champaign entomologist May Berenbaum.

I’m not a smoker and never will be, but I can’t help but be curious about what would happen if I ate a tobacco plant. I don’t have the bad-breath producing gene, but would some essence of nicotine escape from my pores? Or should I just douse myself in nicotine before I head off into the woods? It’s food for thought. Too bad there’s no such thing as tomacco.