Video: Caterpillars Talk With Their Butts

This item requires the Flash plug-in (version 8 or higher). JavaScript must also be enabled in your browser.

Please download the latest version of the free Flash plug-in.

Credit: Jayne Yack

If only world leaders would give this technique a shot. Certain caterpillars of the hook-tip moth family settle their territorial disputes by dragging their butts in a threatening matter. In caterpillars such as Drepana arcuata, seen in this video, a hair-like structure at the end of the abdomen has evolved into an "anal oar" that the insect scrapes along the surface of a leaf to warn off an intruder. (In the video, the defending caterpillar is also drumming and scraping with its mandibles.) You can hear the sound in a quiet room, says biologist Jayne Yack of Carleton University in Canada. "That's how I discovered it—I was rearing them many years ago in my dining room," she says. Some of D. arcuata's relatives crawl at intruders and push, hit, or bite them. The caterpillar's ancestors did that, too, so the scraping movement may have evolved from crawling, Yack and colleagues report online today in Nature Communications.