Breeds of caterpillar found in Arizona include the Empress Leilia, viceroy, mourning cloak, Mexican fritillary and common buckeye. The caterpillar of the Empress Leilia butterfly is green and feeds on trees of the elm family. It hibernates during its third stage.
When the caterpillar of the viceroy hatches, it eats its eggshell and then feeds on the leaves and catkins of the host plants, which are often willows, poplars and cottonwoods. To hide from predators, it gathers leaves and debris and weaves them together with silk.
The caterpillar of the mourning cloak butterfly is black and spiny, with a line of red dots running down its body. These caterpillars can grow up to 2 inches long and often congregate in groups until the first moult. The host plants include poplar, hackberry, American elm and wild rose.
The caterpillar of the Mexican fritillary is bright red with black-edged silver spots. Its body is spiny, and there are two long spines on its head. Its host plants are the foetid passionflower, yellow alder and ipomoea maritima.
The newborn caterpillars of the buckeye are almost black. They are also spiny, with orange- and cream-colored spots. This caterpillar has orange prolegs and overwinters in warm climates such as Arizona's. The host plants include plantains, toadflax, sedum and gerardia.