**White-marked Tussock Moths** (*Orgyia leucostigma*) are common pests of shade trees and fruit trees across eastern North America. The conflict is **defoliation and skin irritation**: the caterpillar is known for its distinctive appearance and wide host range, feeding on the leaves of hundreds of species (especially **elm, apple, oak, and maple**). The hairs on the caterpillar, particularly the long, feathery ones, can cause significant, irritating **allergic dermatitis** upon contact.
Taxonomy and Classification
White-marked Tussock Moths belong to the Order Lepidoptera (Moths and Butterflies) and the Family Erebidae. They undergo complete metamorphosis. The females are unusual because they are entirely wingless and do not fly.
Physical Description
Larvae are 30 mm to 40 mm long.
- **Adult (Key ID):** Male is a small, mottled gray-brown moth with a white spot on the forewing; female is a hairy, wingless, grayish sac that remains near her cocoon.
- **Larva (Key ID):** Striking, brightly colored caterpillar with four dense, white or yellow “tussocks” of hair along its back; two long, black “pencil” tufts near the head and one at the tail.
- **Damage ID:** Chewed or stripped foliage on shade trees; defoliation, particularly in urban areas.
- **Conflict:** Ornamental, Public Health (Irritation).
Distribution and Habitat
Found across Eastern North America. Habitat is urban and suburban shade trees, orchards, and wooded areas. The female lays eggs in a frothy, white mass on her cocoon on the tree trunk.
Behavior and Conflict
The conflict is driven by their hairs and feeding preference.
- **Hairs (Urticating):** The larval hairs are **urticating** (stinging or irritating) and should not be handled; they cause localized rashes upon contact.
- **Host Range:** Their wide polyphagous host range makes them a common sight in gardens and parks.
Management and Prevention
Management is **Mechanical Removal and Biological Control**.
- **Sanitation:** Scraping and destroying the visible egg masses (white foam with pupal cocoon) from tree trunks in the dormant season.
- **Handling:** Never touch the caterpillars with bare skin.
- Application of *Bacillus thuringiensis* (Bt) to young larvae; natural populations are often controlled by parasitic wasps.
Conservation and Research
Research focuses on the role of viral diseases in controlling outbreak populations and the specific allergens present in their defensive hairs.