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Why Do Spicebush Swallowtail Caterpillars Mimic Snakes

The Spicebush caterpillar initially appears as a bird-dropping camouflage, then transforms into a brilliant, bright green “predator” with enormous false “eyes”.

Interestingly, caterpillars have evolved to look and behave the way they do, largely because of predation.

For example, Songbirds, with their keen eyes, are major caterpillar predators, so survival of the fittest favours caterpillars that can fool birds.

Like many caterpillars, the spicebush swallowtail has many defences to protect against this but is best known for its resemblance to a snake, see example below:

It displays false eye spots – “snake eyes” at the front of its snake-like body. The caterpillar’s ruse is enhanced by behaviour.

Prod one and it will rear up in a menacing snake-like posture.

So a fascinating thing about the spicebush swallowtail’s fakery is that it mimics snakes that live thousands of kilometres away.

This works because most songbirds spend about half the year south of Canada (where these caterpillars reside)

When they migrate back to Canada in the spring they pack a menacing visual memory of a tropical threat.

They are also known to spin silk to tighten a leaf around itself, giving the caterpillar a safe place to hide during the day; they resume feeding at night.

Spicebush Swallowtail Caterpillar (snek) - Album on Imgur

Written by Joe Kahlo

After years of writing in the financial industry, Joe was finally able to focus his writing on what he loves, Animals!