Skip over to ScienceNOW to see an amusing piece I wrote about caterpillars talking with their butts. The species I wrote about has a modified hair-like structure, called an anal oar, that it drags across a leaf to make sounds and vibrations that warn off intruders. You can see this in the video that accompanies my story.

The idea is that caterpillars may have evolved this ritualized form of communication out of fighting. The researchers had a neat way of figuring this out – they made a family tree of a few dozen caterpillars. Then, for a few species, they looked at the anatomy of their hind ends and also watched how they defend their territory. Some, the ones that are more like the ancestors, have a leg back there and fight. The anal-scraping ones have no leg on their last segment and never fight. Fighting is dangerous for caterpillars – one bite and they’ll bleed to death. So the territorial displays may have evolved in part to avoid that deadly outcome.

Here’s the paper. It’s open access, so you don’t have to pay to read it, and it’s a pretty good read – much easier to follow than most journal articles I encounter.

Photo: Jayne Yack (video still)