“All swallowtail larvae have an eversible horn-like organ behind the head known as the osmeterium (osmeteria, plural) that looks like a forked snake tongue. It is a bright yellow-orange color on the black swallowtail. When the caterpillar is disturbed it rears up and the organ is extended for a short period of time. When everted it it releases a chemical repellent with a foul smell to repel predators. It is harmless to humans, however.”From Wisconsin Horticulture
One of several black swallowtail caterpillars (all different instars — a younger one pictured below) found munching away on the carrot tops. I wasn’t trying to alarm it into pretending to be a snake, but just my looming presence in the carrot patch was probably a bit alarming.
It would be better for our crisper if the caterpillars were on the usually abundant Queen Anne’s Lace instead of our domestic carrots, but until the wild food gets going, I don’t mind sharing. The veg patch can be a pop-up pollinator garden.