Milkweed Tussock Caterpillar

The milkweed tussock caterpillar is the larval form of Euchaetes egle, a tiger moth (subfamily Arctiinae) native to eastern and central North America. It is one of several insects, along with the monarch butterfly, that specialize on milkweed plants and can tolerate the toxic compounds those plants contain.

Early instars are pale and hairy and feed side by side in clusters, often skeletonizing entire leaves before moving to fresh growth. As they mature, the caterpillars develop the bold tufted coloration for which they are named and begin to disperse and feed individually.

Because milkweed populations support several specialist herbivores, the tussock caterpillar is frequently found sharing host plants with monarch caterpillars, aphids, and milkweed beetles, together forming a distinctive community of milkweed-associated insects.

• Body bears dense tufts of hair arranged in rows: orange near the head and tail, with black and white tufts along the middle of the back
• Reaches about 3.5 cm (1.4 in) in length at maturity
• Younger larvae are paler and less distinctly tufted, often seen feeding in small groups
• Lacks the smooth yellow-black-white banding of monarch caterpillars, which share the same host plant
• Body surface looks fuzzy rather than smooth or striped

This species occurs wherever milkweed (Asclepias species) grows, including meadows, prairies, roadsides, old fields, and garden milkweed patches across the eastern and central United States and adjacent Canada. Caterpillars are most often seen from midsummer into early fall.

Young larvae feed gregariously, clustering on the underside of milkweed leaves and skeletonizing them, while older larvae disperse to feed independently and can consume entire leaves. Like monarch caterpillars, they sequester toxic cardenolides from their milkweed diet, which likely helps make them a less palatable meal for many predators. The species is an important part of the milkweed-associated insect community and a food source for a subset of predators and parasitoids adapted to tolerate its chemical defenses.

Females lay clusters of eggs on the undersides of milkweed leaves. Larvae hatch and feed together through early instars before spreading out as they grow, passing through several molts over a few weeks. Mature caterpillars spin a cocoon incorporating their own body hairs, often at the base of the host plant or in nearby leaf litter, and pupate. Depending on latitude there may be one to two generations per year, with the final generation overwintering as a pupa.