Are We In Danger Yet?
Some caterpillars drag their back ends along leaves to ward off intruders on their territory. Now it seems this “anal-scraping” – which creates warning vibrations – evolved from walking…
It is the strongest evidence yet that communication signals can evolve from the exaggeration and repetition of routine behaviours.
Jayne Yack of Carleton University in Ottawa, Canada, and colleagues compared the genes of more than 30 species of caterpillar. They found that scrapers tended to be species that have evolved more recently, and that they settle disputes with an intruder without fighting. Instead they wiggle their rear, causing oar-like appendages to scrape and drum against the leaf below.