I see these caterpillars in the late summer every year eating apple tree leaves and sometimes black walnut leaves. They are called, for obvious reasons, red-humped caterpillars. Usually they are in small groups of three to six caterpillars or sometimes alone munching away on a leaf. The species name is Schizura concinna and soon they will pupate in the leaf litter passing away the winter. In the spring a moth will emerge looking very much like some piece of gray-brown bark. These moths will lay eggs in the spring on the newly unfolding leaves for the first brood. After the caterpillars pupate and mature into adult moths the eggs of the second or fall brood will be laid. When mature the caterpillars leave the trees and pupate under leaves and grass for the winter. In spring the cycle starts over.
Mature red-humped caterpillars are decked in brown and yellow stripes along the back and wavy white and brown to black stripes along the sides. There are short black tubercles and some short black bristles.
The head and fourth segment are bright red. The fourth segment is enlarged into a hump giving the caterpillar its name. At maturity the caterpillar is between and cm long. Pupa are tan to dark brown. The adults, which are drab grayish brown, are not often seen or noticed.
The red-humped caterpillar moth is a wide ranging species from southern Canada to Florida and west to California.
Class Insecta (Insects)
Order: Lepidoptera (Butterflies and Moths)
Suborder: Glossata (All moths and butterflies with a coilable proboscis)
Infraorder: Heteroneura (Moths and butterflies with wing venation not the same on both pairs of wings)
Superfamily: Noctuoidea (Owlet Moths)
Family Notodontidae (Prominent Moths)
Subfamily: Heterocampinae (A subfamily of the prominent moths)
Genus and Species: Schizura concinna
Essig, E. O., Editor (1913). The Red-humped Caterpillar in Injurious and Beneficial Insects of California, 2 (1, 2):188.