During one of my regular wanderings of the garden I spotted a Giant Swallowtail (Papilio cresphontes) caterpillar on a Common Rue (Ruta graveolens), which is one of its host plants. Given the size of this caterpillar (nearing pupation, I think), it must have been there a while and I just hadn’t noticed it before.
As I reached down to move a leaf to get a better look, suddenly the caterpillar popped out a bright orange V-shaped structure from its head. Clearly it was startled, and so was I! After a short time (less than a minute), the structure was retracted. According to Texas A&M AgriLife Extension, “When disturbed, [Giant Swallowtail] caterpillars display a pair of horn-like, orange glands (osmeteria) which emit a foul smell.” I didn’t smell anything from the distance I was away from it.
Giant Swallowtail caterpillars have also been called “bird poop” caterpillars because of their shape and coloration, and presumably this helps with disguise from predators. But I had no idea they had alarm signals as well, which was something new for me to learn!
Below are photos of this caterpillar with and without its osmeteria activated, and the first photo of this post is another picture of the activation.
Rewilding My Lot 
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