It looks like an unassuming twig: brown, knobbly, modest. 'What great camouflage for a caterpillar in a rainforest—no one would ever find that,' you might think. And you’d better think it, because as soon as you open your mouth: BOING! Out shoots four white-tipped tentacles from its back!
Slowly, they recoil in towards the body, primed and ready to eject back out again at the slightest disturbance. This bizarre caterpillar and its odd defense mechanism was found by Aaron Pomerantz, an entomologist working for an ecotourism company in the Peruvian Amazon. He spotted the creature about 100 feet (30 meters) up a tree near the Tambopata Research Center when he shouted down to his friends and noticed its extraordinary response to his voice. He then spent over an hour with his friends shouting at the animal and filming its response.
Pomerantz thinks that it belongs to the genus Nematocampa, as other members of the group also have weird twirly tentacles sprouting from their backs. These particular caterpillars can be found in North America and throughout the Neotropics. But as for the reasons for their protrusions, and in particular this little guy's response to sound, well that’s a little trickier to explain.
One possibility is that they mimic the movement of a falling flower in the wind. Another could be that when the caterpillar shoots out its tentacles, it hopes a predator might pluck one of them off, allowing it to get away. Or it could be to simply scare away any potential predator or parasite. The truth is, no one really knows.