for D E C E M B E R Winter Moth PROPER NAME: Operophtera brumata WHEN MOST PREVALENT: Winter moth get their name because adults emerge from the pupal stage after the first frosts of the winter. They are common as adults in late November through December. The next time members of this species will be common is in late March through late May when the caterpillars hatch from eggs and feed on the leaves of a variety of trees and bushes - oaks, apples, birch, blueberries, etc. SIZE RANGE: Adult females are wingless and approximately 10 to 12 mm in length. Males have slender bodies and a wing spread of 25-30mm. They are both brown. Sorry, we do not have a magnified view of the winter moth WARNINGS: These insects are harmless but in some circumstances they can cause considerable damage as larvae to leaves of trees. GEOGRAPHIC LOCATION: Throughout Canada SOUNDS: None Winter moth are native to western Europe and Britain but were accidentally introduced to Canada, first to Nova Scotia in the 1950s and then to Victoria, B.C. in the 1960s. They have since spread to Vancouver. The female moths crawl up tree trunks after emerging from pupae in the soil. They attract males with a chemical perfume (pheromone) and, after mating, lay eggs under lichens and in cracks in the tree bark. Eggs hatch in the early spring just as the leaves are expanding. Tiny larvae move among trees by spinning down on silk threads and blowing in the breeze (ballooning). Larvae feed for several months and then drop from the tree to pupate in the soil. Ground beetles eat a high proportion of the pupae over the next several months and help control the winter moth populations. Winter moth populations were very high after their introduction to Canada and they caused severe defoliation particularly to urban trees. A parasitoid fly, Cyzenis albicans, was introduced as a biological control agent and seems to work in conjunction with the ground beetles to reduce winter moth populations. This fly is attracted to damaged leaves where it lays eggs which are eaten by the caterpillars. Fly larvae eat the caterpillars from the inside and and kill them after the caterpillars drop from the tree. Because the females must walk up trees to lay eggs, they can be captured on bands of sticky tape wrapped around tree trunks. Although this kills many moths, the "ballooning" behaviour of larvae after they hatch from eggs in the spring means that trees will not be completely protected. FAMILY RELATIONS a) Order Lepidoptera, Family Geometridae - geometers or inchworms. b) Close cousin: Bruce's spanworm, Operophtera bruceata - native to Canada. [TO TOP] [HOME]