Annette Aiello, an entomologist with the Smithsonian, has provided me with the following excellent information concerning the caterpillar we found in the Pelliciera forest of Peninsula Valiente (see June 22 post).
“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).”
John Christy, a fiddler crab expert I met in Panama (more about his work in a later post), adds the following comment:
“Kennedy – that is an amazing (!!) caterpillar, complete with liverwort-like patterning. It would seem to be highly specialized. You may well have something new. I wonder if the pattern mimics a particular snake? A quick google search produced Liophis cobellus as a “mangrove snake” of South America. It is a colubrid and looks vaguely like the caterpillar.”