Forest and Western Tent Caterpillars
(Malacosoma disstria & M. californicum)
Damage: Fully enclosed tents or silken mats are built from May to June by groups of hundreds of caterpillars. Entire branches or bushes can be defoliated.
Insect: Tent caterpillars are covered in long hairs and grow up to 30 mm long. Both species have significant markings such as blue lines and white diamonds along the back of Forest Tent Caterpillars. Western tent caterpillars are mostly orange and black with pale blue marks along the back. Tent caterpillars feed together in large groups until pupation in mid- summer. Moths are tan coloured, fly in summer, and lay overwintering egg masses on tree branches. Egg masses are protected by grey-black spongy material, which looks and feels like grey Styrofoam. One generation per year.
Damage: Small webbed tents appear at branch tips in early July. These tents contain hundreds of caterpillars. The tents and caterpillars grow in size and can encompass an entire bush by September. Entire branches are defoliated inside the webbing.
Insect: Caterpillars are commonly light coloured with long pale hairs. Caterpillars have black spots and dark heads, and the larvae body may darken with age. Larvae grow up to 35 mm in length. Moths are mostly pure white, and fly in early summer. They lay egg masses on the underside of leaves and cover with hairs. Eggs hatch within a week. Once larvae are mature, they crawl to protected areas on the tree or in leaf litter, to overwinter as a pupae. One generation per year.