Saturday, February 12, 2011

Noisy Caterpillars

Image via Live Science video
When the Huffington Post writes about caterpillars, you know the story "has legs".  It turns out that caterpillars can be noisy - we just hadn't been listening closely.

Initially reported online in the Journal of Experimental Biology by Jayne Yack and Veronica Bura,  Live Science describes research on Walnut Sphinx caterpillar's ability to whistle.  Unlike a wolf whistle which is used to attract mates, these creatures use their whistle to ward off predators.

The Walnut Sphinx Moth is "highly common across Missouri with limited appearances in certain portions of other states east of the Rocky Mountains.  Like some other moths, the adults do not feed, living only long enough to breed.
Walnut Sphinx Moth- Wikimedia

How does a caterpillar whistle when it doesn't have lungs?  They use their spiracles, small holes in their sides where they get their air.  By applying latex to each pair of spiracles, researchers found that the eighth pair are the noisy ones.

Some silk-moth caterpillars make a clicking sound by snapping their mandibles together, warning off predators.  Suspecting a similar motive in the whistles, Yack and Bura put walnut sphinx caterpillars in cages with birds which eat them.  When the birds approached, the caterpillars whistled and the birds backed off.  No caterpillars were harmed in these experiments (besides scaring the whistle out of them.)

Other caterpillars defend their territory by scraping their rear ends (called "anal oars") against leaves, making a sound to announce their territory.  (I am not going there.)

The recording in this LiveScience video probably won't make the Grammys, but it does prove that the walnut sphinx caterpillars aren't just whistling Dixie.

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