Black swallowtail caterpillar

Description:

This caterpillar absorbs toxins from the host plants, and therefore tastes poor to bird predators. The Black Swallowtail caterpillar has an orange "forked gland", called the osmeterium. When in danger, the osmeterium, which looks like a snake's tongue, everts and releases a foul smell to repel predators. - from Wikipedia