Snake Fake

Photograph by Mark Bowler

Story by Madison Pobis

As a sphinx moth caterpillar (Hemeroplanes triptolemus) grows and molts, storing energy from the leaves it consumes, a kaleidoscopic blend of brown and white patches keep it camouflaged amidst the foliage it calls home. The larger the caterpillar grows, however, the harder it becomes to hide. Fortunately for this particular species, its final stage of development offers a new strategy for protection—one intimidating enough to deter even the most ambitious rainforest predator.

At the slightest hint of danger—be it a stooping bird or pouncing lizard—the sphinx moth caterpillar begins its masquerade. Dangling from a twig, it reveals an underside patterned in faux snakeskin and eyespots that appear to glisten. By sucking in air through tiny holes in its surface, the caterpillar inflates its head to create the illusion of a triangular skull swollen with venom glands. If the shape of a deadly snake isn’t enough to startle away a hungry predator, the caterpillar will lunge as if to strike. And despite the larva’s comical lack of any actual weaponry, the strategy appears to be effective. In experiments using artificial caterpillars made out of pastry dough, researchers have found that eyespots and a snake-shaped head can greatly improve a caterpillar’s odds of survival among avian predators, even in regions where tree-dwelling snakes are rare.

Other caterpillars in the sphinx moth family have evolved similar tactics for surviving the stages of development when they are most vulnerable to predators. Nessus sphinx moths (Amphion floridensis), for example, emit an alarming shriek by forcing air through modified mouth parts whenever they’re disturbed, and many larvae will vomit toxic foregut contents onto pesky parasites. These evolutionary strategies have helped to ensure that caterpillars will survive and eventually emerge as fluffy moths ready to mate, pass their adaptations along to the next generation, and of course pollinate flowers, helping to secure not only their own species’ survival but that of countless plants as well.

Amarakaeri Communal Reserve, Peru

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