June 22nd, 2009

Ay caramba! A caterpillar that thinks it’s a snake


Today we found a caterpillar that belongs in the Guinness Book of Records in the “most bizarre” category. About 8 cm long and as thick as my little finger, it had a head like a snake, which it would lift up if you breathed on it. The tail end had a single Cyclops eye in the middle of it, complete with a fake eyelid that blinked.

The creature was positioned head-down on the trunk of a Pelliciera (perhaps so that a predatory bird would be attracted to the eye, the “decoy”). Pelliciera trunks here are covered with mats of tufting liverworts, which are favourite haunts of tree crabs. The trunk was bare around the caterpillar’s head, and looked to have been grazed by the animal.

I’m working on finding out what sort of moth or butterfly this magnificent beast turns into, but if it’s even half as spectacular as its larvae it must be quite a sight.*

(Click photo to see more pictures of the “snake caterpillar of Valiente.”)

Contender for the 'most bizarre' award?

Contender for the 'most bizarre' award?

*UPDATE Annette Aiello, an entomologist with the Smithsonian, has provided me with the following excellent information:

“My guess is that your spectacular caterpillar belongs to the moth family Sphingidae, the sphinx moths, which include the well-known ‘tomato horn worm.’ Several sphingid genera are snake mimics, and in most of the cases I’ve seen so far, it is the ventral surface of the body that is displayed to resemble a snake. You can see that in the attached photograph of a species of Hemeroplanes. The head, mostly hidden, forms the blunt nose of the snake, then behind that you see the ventral surface of the thorax with its three pairs of true legs folded against the body, and the large, dark, false eyes (that can be opened and closed with blood pressure) on the sides of the third thoracic segment. Continuing back, you see the first three pairs of false legs (prologs), which are the large black structures on the ventral surface of the abdomen. The larva is holding on to the substrate with its fourth pair of prologs. In contrast, your caterpillar presents its dorsal surface during the display. The only record I can find of a similar caterpillar is Pholus labruscae, shown figure d, plate xiii of Miles Moss (1912) publication “On the Sphingidae of Peru,” Transactions of the Zoological Society of London 20(2): 73-134. Moss describes the final stage larva as ‘Remarkably snake-like, either end appearing as the head of a snake.’ He reports that the caterpillar eats members of the grape family (Vitaceae).”

Pholus labruscae

Pholus labruscae

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