A caterpillar in the Amazon has just created the perfect defense against the ‘stop and chat’: any noise causes it to fire four spiraling tentacles on its abdomen – the cranky bug version of “leave me alone.”

“I had just climbed to the top of a canopy tower overlooking the rainforest when I called to my group below me, when suddenly a flash of movement at eye-level caught my attention,” recalls entomologist Aaron Pomerantz, who happened upon the creature while traversing the jungles of Peru. Given the larva’s strange aversion to conversation, Pomerantz took the only logical next step and yelled at it again. For an hour. Because science.

“Screaming at caterpillars doesn’t fall into most people’s job descriptions,” he says. “But this reaction to noise was so peculiar that once my group joined me, we took turns yelling at it and filmed its contorting reactions…all to bring the story of this bizarre organism to you!”

A bit of digging revealed the caterpillar belongs to the Nematocampa genus of moths, which use hemolymph – the insect equivalent to blood but grosser– to enlarge the long appendages until they become erect (sound familiar?).

The strange defense has been observed before, but there are a lot hypotheses about its origin. It’s possible that the filaments help the larva blend in, mimicking the way a flower’s stamens would blow in the wind. “It could also be that the tentacles extend when the caterpillar is alarmed so that an attacking predator (such as a bird) has a higher probability of snagging a tentacle, as opposed to the main body (similar to how some lizards are able to lose their tails),” explains Pomerantz. Further still, the tips of the tentacles are covered with tiny hairs, called setae, which could act as highly sensitive vibration detectors, allowing the caterpillar to hear incoming threats before they come into view.

It’s a bit of a mystery, but one thing’s for sure, we’ve never wanted to yell at a caterpillar so badly.

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IMAGES: Aaron Pomerantz, Steven Senisi and Dr. Andrew Warren