The Anal Howitzer; or, Frass-A-Blast!

[peristaltor]

That post on lice evolution led me to explore The Loom, Carl Zimmer's Science Blog, which led me to buy his book, Parasite Rex. So far, it's a great introduction to pests.

Something I read today got me chuckling maniacly.

(Leaf-rolling caterpillars are) pretty ordinary insect larvae with one exception: they fire their droppings like howitzers. As a bit of frass starts to emerge from the caterpillar it pushes a hinged plate back against a ring of blood vessels surrounding the anus. The blood pressure builds up behind the plate, which the caterpillar then releases. The pressure of the blood slams against the droppings so suddenly that it blasts them three feet a second, in a soaring arc that carries them up to two feet away. (Zimmer, Parasite Rex, Touchstone, 2001, p. 180)

"Back off, predator! I've gotta poo!"