A little while ago I said I'd see if I could get a picture of a mature black swallowtail caterpillar's methods of self defense. You remember they start out mimicking a bird dropping, then grow to their mature appearance (such as the ones here) where they rely on their coloring to blend in with the surroundings.
However, if a predator does spot them and they are threatened, these caterpillars will extend a forked orange protuberance from just behind their heads. It looks like a snake tongue, and emits a foul odor. You can see the second caterpillar in the picture doing that here.
Be assured no caterpillars were harmed in taking these pictures. I squeezed very gently (the big guy never would do it, no matter how much I poked and prodded) and then left him alone to eat away.