Whistle while you try not to be eaten?

This is Sandra Tsing Loh with the Loh Down on Science.

Caterpillars are known-among researchers at least-for making clicking or squeaking sounds. Unless you're a walnut sphinx caterpillar, in which case, you whistle.

As caterpillars don't have lips or noses, though, how do they whistle?

Scientists from Ottawa's Carleton University wanted to find out. They focused in on small holes, or spiracles, in the caterpillar's side. Caterpillars breathe through them, so the holes seemed the likely candidate.

The researchers covered all eight spiracle pairs with latex. The holes were uncovered one pair at a time, as the caterpillars' bodies were pinched to force air out. At the eighth pair? Out came a tuneful tweet.

Why whistle? Self-defense, of course. That was proven when walnut sphinxes were put into cages with caterpillar-eating birds. Any time a bird approached, the caterpillars blew their body whistles--and foes instantly backed off.

Apparently, just being able to whistle doesn't guarantee a happy tune--but for caterpillars, anyway, it can make for a happier ending.



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