Backyard Science: The Black Swallowtail Caterpillar

As many people know, black swallowtail caterpillars feed on dill. Below, you can see two caterpillars on the same dill plant. They look very different from each other. The small one is a first instar, or the first in a succession of molts as the caterpillar grows to maturity. The larger caterpillar is in its second or third instar. You can tell because it still has spikes on its back. Both will (with luck) become black swallowtail butterflies.

Just 48 minutes after shooting the third instar caterpillar I took another picture showing it had just molted. The old shriveled exoskeleton is on the stem just below the caterpillar

Roger Inman