LD Moth (Lymantria dispar) — identification, habitat & look-alikes

LD Moth, more commonly known in the United States as spongy moth, is an moth whose caterpillars can strip leaves from hundreds of kinds of trees and shrubs. Its fuzzy egg masses can be carried to new areas on firewood, vehicles, and outdoor furniture. Spongy moth caterpillar hairs can irritate skin, so avoid handling the caterpillars with bare hands.

Appearance

Appearance: Mature caterpillars are hairy, about 1.5–2.5 in (4–6 cm) long, and usually show five pairs of blue bumps followed by six pairs of red bumps. Adult males are smaller and brown; females of the established U.S. are larger, pale, and flightless.

Look-alikes

fall webwormHyphantria cunea

Fall webworm caterpillars are pale yellow to brown and feed inside conspicuous silk webs, usually later in summer. Spongy moth caterpillars do not make tents and have paired blue and red bumps.

Why they get mixed upBoth are hairy tree-feeding caterpillars that can be numerous.

eastern tent caterpillarMalacosoma americana

Eastern tent caterpillars have a solid pale stripe down the back and live in silk tents in branch forks. Spongy moth caterpillars lack the stripe and do not build tents.

Why they get mixed upBoth hatch in spring and are dark, hairy caterpillars on trees.

Where it lives

Typical habitats: deciduous forests
wooded neighborhoods
parks
orchards
Range: Established populations occur mainly in the Northeast and parts of the Great Lakes and upper Midwest. Federal and state programs work to slow its spread beyond d areas. It is managed as an invasive pest in the United States.
Preferred conditions: Caterpillars are especially common where preferred hosts such as oaks are abundant. Egg masses can survive on many sheltered outdoor surfaces.
When to see it: In Iowa
Active Jul–Aug

Behavior

Diet: Caterpillars eat leaves from oaks and many other trees and shrubs.
Activity: Eggs hatch in spring, caterpillars feed through early summer, and adults appear in summer. The species has one generation each year.
Overwintering: The insect spends winter as eggs in buff or tan, felt-like masses attached to bark or outdoor objects.

Life cycle

Clutch size: A fuzzy tan egg mass can hold about 500–1,000 eggs.
Caterpillar food plants: Caterpillars feed on more than 300 kinds of trees and shrubs. Oaks are especially important hosts, but they also use aspens, birches, willows, apples, and others.

Cautions

Cautions: Caterpillar hairs can irritate some people's skin. Avoid bare-handed contact.

Name and classification

About the name: The established U.S. subspecies is Lymantria dispar dispar. Females of the Asian subspecies L. d. asiatica and L. d. japonica can fly; those subspecies are not established in the United States.

Conservation

IUCN Red List: NENot EvaluatedNot yet assessed
Threats: Repeated heavy weakens trees and can contribute to tree death, especially when drought, disease, or other pests add stress.

Culture and stories

Culture and stories: The name spongy moth refers to the sponge-like appearance of its egg masses.
Moving firewood and outdoor belongings can carry egg masses into new areas, so movement from quarantine zones is regulated.

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