Tussock Moth Caterpillars

These Itsy-Bitsy Critters Can Eat Their Way Through Entire Forests

The rusty tussock moth caterpillar

 mikroman6/Getty Images

Tussock Moth caterpillars (from the family Lymantriidae) are voracious eaters capable of defoliating entire forests. The best-known member of this family is the beautiful but highly detrimental Gypsy Moth which is not native to North America. After its introduction, the potential for destruction these critters could wreak became all too clear. In the United States, the Gypsy Moth alone costs millions of dollars to control each year.

To insect lovers, however, Tussock Moth caterpillars are known for their striking tufts of hair, or tussocks. Many species exhibit four characteristic clumps of bristles on their backs, giving them the appearance of a toothbrush. Some have longer pairs of tufts near the head and rear. Judged on looks alone, these fuzzy caterpillars might appear harmless but touch one with a bare finger and you'll feel as if you've been pricked by fiberglass. Some species, such as the Brown-tail, will even leave you with a persistent and painful rash. Tussock Moth adults are often dull brown or white. Females are usually flightless, and neither males nor females feed as adults. They focus on mating and laying eggs, after which they die within days.

White-Marked Tussock Moth

Whitemarked Tussock Moth Caterpillar
Laszlo Podor / Getty Images

The White-Marked Tussock Moth is a common native of North America and is found throughout the eastern United States and Canada. These caterpillars feed on a range of host plants, including birch, cherry, apple, oak, and even some coniferous trees like fir and spruce, and may cause damage to trees when present in significant numbers.

White-Marked Tussock Moths produce two generations each year. The first generation of caterpillars emerges from their eggs in springtime. They feed on foliage for four to six weeks before pupating. After two weeks, the adult moth emerges from the cocoon, ready to mate and lay eggs. The cycle is repeated, with the eggs from the second generation overwintering.

Browntail Moth

Nest of the Brown-Tail (Euproctis chrysorrhoea) on Sea-Buckthorn

Mantonature / Getty Images

Browntail moths (Euproctis chrysorrhoea) were introduced into North America from Europe in 1897. Despite their initial rapid spread throughout the Northeastern United States and Canada, today they are only found in small numbers in some New England states, where they remain persistent pests.

The Browntail caterpillar is not a picky eater, chewing on leaves from a variety of trees and shrubs. In large numbers, the caterpillars can quickly defoliate host plants in the landscape. From spring into summer, the caterpillars feed and molt. They reach maturity in mid-summer, at which time they pupate on trees, emerging as adults two weeks later. The adult moths mate and lay eggs that hatch by early fall. Browntail caterpillars overwinter in groups, sheltering in silken tents in the trees.

Warning: Browntail caterpillars have tiny hairs known to cause a severe rash in humans and should not be handled without protective gloves.

Rusty Tussock Moth

Orgyia antiqua Rusty Tussock Moth larva (Orgyia antiqua)

USDA Forest Service Archive, USDA Forest Service, Bugwood.org/Wikimedia Commons/CC-SA-3.0

The Rusty Tussock Moth (Orgyia antiqua), also known as the Vapourer Moth, is native to Europe but can now be found throughout North America and Europe, as well as parts of Africa and Asia. This European invader feeds on both foliage and bark from trees including the willow, apple, hawthorn, cedar, Douglas-fir, and an assortment of other trees and shrubs. On coniferous trees, the caterpillars feed on new growth, devouring not only the needles but the tender bark on twigs.

Like many other Tussock Moths, Orgyia antiqua overwinters in the egg stage. A single generation lives each year, with the larvae emerging from eggs in spring. Caterpillars may be observed throughout the summer months. Male adults fly during the daytime, but females cannot fly and lay their eggs in a batch over the cocoon from which they emerged.

Gypsy Moth

Lymantria dispar Gypsy Moth larva (Lymantria dispar)

University of Illinois/James Appleby/Wikimedia Commons/CC-SA-3.0

The Gypsy Moth was first introduced into the United States around 1870​. Its subsequent widespread population and voracious appetite make it a serious pest in the eastern United States. Gypsy Moth caterpillars feed on oaks, aspen, and a variety of other hardwoods. A heavy infestation can leave summer oaks completely stripped of foliage. Several consecutive years of such feeding can kill trees entirely. in fact, the Gypsy Moth ranks as one of the "100 of the World's Most Invasive Alien Species," according to the World Conservation Union.

In spring, the larvae hatch from their winter egg masses and begin feeding on new leaves. Caterpillars feed primarily at night, but in a year of high Gypsy Moth populations, they may continue feeding through the day as well. After eight weeks of feeding and molting, the caterpillar pupates, usually on tree bark. Within one to two weeks, adults emerge and begin mating. The adult moths do not feed. They live only long enough to mate and lay eggs. The larvae develop within the eggs in the fall but remain inside them over the winter months, emerging when buds start to open in spring.

Nun Moth

Lymantria monacha Nun Moth larva (Lymantria monacha)

Louis-Michel Nageleisen, Département de la Santé des Forêts, Bugwood.org/Wikimedia Commons/CC-SA-3.0

The Nun Moth (Lymantria monacha), is one Tussock Moth native to Europe that has not made its way to North America. That's a good thing because in its native range it has wreaked havoc on forests. Nun Moths like to chew the base of needles on coniferous trees, allowing the rest of the untouched needle to fall to the ground. This eating habit results in extensive needle loss when caterpillar populations are high.

Unlike many other species of Tussock Moths, both males and females are active fliers. Their mobility allows them to mate and lay eggs over wider ranges of their forest habitat—which unfortunately increases the spread of defoliation. Females deposit eggs in masses of up to 300 which overwinter in the egg stage. The larvae emerge in spring, just when tender new growth appears on the host trees. This single generation devours foliage as it passes through as many as seven instars (the phases between two periods of molting in the maturation process of an insect larva or other invertebrates).

Satin Moth

Leucoma salicis Satin Moth larva (Leucoma salicis)

Gyorgy Csoka, Hungary Forest Research Institute, Bugwood.org/Wikimedia Commons/CC-SA-3.0

The Eurasian native Satin Moth (Leucoma salicis) was accidentally introduced to North America in the early 1920s. The original populations in New England and British Columbia gradually spread inland but predation and parasites seem to be keeping this insect pest largely under control.

The Satin Moth has a unique life cycle with one generation each year. Adult moths mate and lay eggs in the summer months and caterpillars hatch from those eggs in the late summer and early fall. The tiny caterpillars feed for a short while—most often on poplar, aspen, cottonwood, and willow trees—before they retreat inside bark crevices and spin a web for hibernation. Satin Moths overwinter in the caterpillar form, which is unusual. In spring, they re-emerge and feed again, this time reaching their full size of nearly two inches prior to pupating in June.

Definite-Marked Tussock Moth

Orgyia definita Definite Marked Tussock Moth larva (Orgyia definita)

Forestry Archive, Pennsylvania Dept. of Conservation and Natural Resources, Bugwood.org/Wikimedia Commons/CC-SA-3.0

The Definite-Marked Tussock Moth (Orgyia definita) has a common name almost as long as the caterpillar. Some refer to the species as the Yellow-Headed Tussock, however, along with having a yellow head, this caterpillar's toothbrush-like tufts of hair are a striking yellow as well. Whatever you want to call them, these caterpillars feast on birch, oak, maples, and basswoods throughout the eastern United States.

Moths emerge from cocoons in late summer or early fall, when they mate and deposit their eggs in masses. The females cover their egg masses with hairs from their bodies. Definite-Marked Tussock Moths overwinter in egg form. New caterpillars hatch in spring when food becomes available again. Through most of its range, the Definite-Marked Tussock Moth produces one generation per year but in the southernmost areas of its reach, it may produce two generations.

Douglas-Fir Tussock Moths

Orgyia pseudotsugata Douglas Fir Tussock Moth larva (Orgyia pseudostugata)

Jerald E. Dewey, USDA Forest Service, Bugwood.org/Wikimedia Commons/CC-SA-3.0

The caterpillar of the Douglas-Fir Tussock Moth (Orgyia pseudotsugata) feeds on firs, spruce, Douglas-firs, and other evergreens of the western United States and are a major cause of their defoliation. Young caterpillars feed exclusively on new growth but mature larvae feed on older foliage as well. Large infestations of Douglas-Fir Tussock Moths can cause severe damage to trees—or even kill them.

A single generation lives each year. The larvae hatch in late spring when new growth has developed on the host trees. As the caterpillars mature, they develop their characteristic dark tufts of hair at each end. In mid to late summer, caterpillars pupate, with the adults making their appearance from late summer to fall. Females lay eggs in masses of several hundred in the autumn. Douglas-Fir Tussock moths overwinter as eggs, entering a state of diapause (suspended development) until spring.

Pine Tussock Moth

Dasychira pinicola

USDA Forest Service, Bugwood.org/Wikimedia Commons/CC-SA-3.0

While the Pine Tussock Moth (Dasychira pinicola) is native to North America, it's still a species of concern to forest managers. Pine Tussock Moth caterpillars feed twice during their life cycle: late in summer and again the following spring. Predictably, Pine Tussock Moth caterpillars feed on pine foliage, along with other coniferous trees such as spruce. They prefer the tender needles of jack pine, and during years of high caterpillar populations, entire stands of these trees may be defoliated.

The caterpillars emerge in the summer months. Like the Satin Moth, the Pine Tussock Moth caterpillar takes a break from feeding to spin a hibernation web and stays inside this silk sleeping bag until the following spring. The caterpillar finishes feeding and molting once warm weather returns, pupating in June.

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Hadley, Debbie. "Tussock Moth Caterpillars." ThoughtCo, Aug. 31, 2021, thoughtco.com/tussock-moth-caterpillars-4097354. Hadley, Debbie. (2021, August 31). Tussock Moth Caterpillars. Retrieved from https://www.thoughtco.com/tussock-moth-caterpillars-4097354 Hadley, Debbie. "Tussock Moth Caterpillars." ThoughtCo. https://www.thoughtco.com/tussock-moth-caterpillars-4097354 (accessed June 10, 2023).