This Crazy Caterpillar Has Tentacles That Erupt When You Yell at It


On my recent travels through the Peruvian Amazon, I came upon the craziest caterpillar that I have ever seen, and subsequently yelled at it for hours.

Why did I yell at it? Well, its strange behavior toward sound was why I noticed it in the first place. I had just climbed to the top of a canopy tower overlooking the rainforest when I called to my group below me — suddenly a flash of movement at eye-level caught my attention.

On a nearby tree branch hung a caterpillar with four strange tentacle-like appendages protruding from its abdomen. I might never have noticed this small brown insect had it not been for its unusual movement: noises would cause it to fire its tentacles in randomized directions, then slowly twirl back into a spring-like “ready” position to await its next alarm. This reaction to noise was so peculiar that once my group joined me around the creature, we proceeded to take turns yelling at it and filming its contorting reactions for over an hour.

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After a little research, I found that this caterpillar is in the moth family Geometridae and is in the genus Nematocampa. Also referred to as “horned spanworms” or “filament bearers,” these peculiar caterpillars can be found in North America and the Neotropics.

David Wagner, in his field guide “Caterpillars of Eastern North America,” notes:

It is difficult to imagine what the [Nematocampa] larva is mimicking, but the overall effect is not unlike a fallen brown flower with exerted stamens. Alarmed caterpillars shunt hemolymph into filaments, enlarging them by as much as twice their resting length.

What Wagner seems to be proposing is that the larva movement is similar to the way flowers or other plant matter move in the wind: the —> Read More