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Nature In The Natural State: Giant Swallowtail Caterpillars

Three small wafer ash trees grew in a yard, planted to be host plants for butterflies. This year, in mid-August, a giant swallowtail butterfly mother laid eggs on the leaves over a period of days. Caterpillars soon hatched and began munching on the leaves.

They are called “bird poop” caterpillars because that’s what they look like. But their large thorax resembles a snake’s head, and if you disturb them, they rear their heads back sharply, emitting a pungent odor, and two red horns, the osmeterium, shoot out of their foreheads. All these qualities frighten away would-be predator birds.

Members of the last brood of the year, each one will form a chrysalis on either their or nearby trees, where they will spend the winter and emerge in spring, as the largest butterflies in Arkansas.