Lymantria dispar

Lepidoptera - Moths and Butterflies

Adults are large moths with black, wavy lines on the forewing and a distinctive ‘V’ -shaped marking. Males are light to dark brown while females are white and flightless (though they do have wings).

Early instar larvae are dark and very hairy with large heads. Most larvae are black although brown larvae have been seen in southern Ontario. Larvae have rows of blue and red dots along their back that become more noticeable as they mature. Early instar larvae have dark heads and mature larvae heads are light yellow with many black markings. Long, fine yellow and black hairs arise from tubercles along the sides of the caterpillar. Larvae will often hide on the undersides of leaves, branches or in bark crevices during the day.

Eggs are laid in thumb-sized, fuzzy masses of over 500 individuals and are covered with tan-coloured hairs.

Acer spp. (maple)
Fagus spp. (beech)
Malus spp. (crabapple)
Picea spp. (spruce)
Populus spp. (poplar)
Quercus spp. (oak)
Tilia spp. (linden)
Thuja spp. (cedar)

Larvae chew on foliage. Early instars make small holes in foliage while older larvae may consume the entire leaf except the main veins.

Eggs hatch between early April to late May. Larvae disperse by catching wind while suspending themselves on a line of silk. Larvae feed for about 7 weeks, usually at night. In the daytime, larvae descend from the canopy and seek shelter on the trunk. Pupation occurs in sheltered places, often on the bole of the tree. Pupae are brownish black and are often accompanied by shed larval skins. Male moths emerge in July, usually a few days before females. Males are active fliers while females are flightless. Once mated, females crawl up the trunk to lay eggs on the trunk and undersides of branches. The egg masses overwinter.

Johnson, W.T. and Lyon, H.H. 2003. Insects That Feed on Trees and Shrubs. Second Edition. Cornell University Press, Ithaca, New York. 560 pp.