Appearance

Appearance

Wingspan about 1.4–2.2 in (35–55 mm); females are larger. The forewings are white crossed by many black zigzag lines. Females have a reddish-brown abdomen with black spots; males have feathery antennae. Dark gray-brown to nearly black forms also occur.

Look-alikes

LD moth (spongy moth)Lymantria dispar

Male LD moths are dark brown, and females are off-white with faint markings; they cover their egg masses with fuzzy hairs. Nun moths have crisp black zigzag lines on white forewings and lay bare eggs in bark cracks.

Why they get mixed up · Same genus, similar hairy caterpillars with blue bumps, and both can be serious forest pests.

Where it lives

Typical habitats

• conifer forests
• mixed forests

Range

Native across temperate Eurasia, from Europe to East Asia, including Korea and Japan. Not established in the US or Canada.

Behavior

Diet

Caterpillars eat the needles and leaves of many trees, especially spruce, pine, fir, larch, and Douglas-fir, as well as oak, birch, maple, and fruit trees such as apple.

Overwintering

Overwinters as eggs tucked into bark crevices; one generation per year.

Life cycle

Larva

Mature caterpillars are about 1.2–2.4 in (30–60 mm) long, brown and hairy, with two rows of bluish bumps along the back, orange warts in the middle of the back, and a dark stripe down the back.

Connected species

Caterpillar food plants

• sprucesPicea

  A preferred host; European outbreaks are often in Norway spruce stands.

• pinesPinus

  Another preferred host, especially Scots pine in Europe.

Conservation

IUCN Red List

NENot Evaluated·Not yet assessed

Threats

Egg clusters can hitch rides on logs, wood packaging, shipping containers, and ships, which is the main way it could reach North America. Its broad taste in trees, including several North American conifers, is why an introduction is a concern.