LIFE CYCLE OF LAMBDINA ATHASARIA (WALKER) (LEPIDOPTERA: GEOMETRIDAE) DEVELOPING ON HEMLOCK IN CONNECTICUT

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Abstract
During 1992 and 1993, we studied the life cycle of Lambdina athasaria (Walker) developing on eastern hemlock, Tsuga canadensis (L.) Carrière, in Connecticut. The geometrid was univoltine, overwintering as a pupa. Adults emerged during 4 weeks in May and June after hemlock budbreak. Males emerged significantly earlier than females, and both sexes emerged earlier in 1993 than in 1992. Males flew for 4–5 weeks annually. Based on measurements of head capsule width, larvae had five or six instars, which fed from June to October. Early instars ate new growth, and older ones fed on old growth. Until mid-August, larval development was more advanced in 1993 than in 1992. Larvae descended from trees in September and October to pupate in the duff beneath trees. Lambdina athasaria can be distinguished from congeneric species that feed on conifers by its overwintering stage, flight period, larval size, and host.