The giant swallowtail caterpillar has quite the defense when bothered. They have an osmeterium, which is a Y-shaped eversible gland, that is used to wipe against small predators, such as ants and spiders. When the caterpillar is in its fourth and fifth instars it contains a highly noxious, pungent mixture of chemicals, which has a very distinctive smell.

This giant is in our butterfly house. When I was moving around plants, it brushed the caterpillar sending him into defense mode. And, yes, there was a pungent smell that filled the space.