Forest edge effects on the biological performance of the forest tent caterpillar (Lepidoptera : Lasiocampidae) in sugar maple stands

Fragmentation of forests has considerably increased the amount of edge habi tats. This edge effect could have a direct influence on the dynamics of for est insects by altering the nutritional quality of Foliage. In this study, we examined from 1994 to 1997 the effects of foliage from edge trees and in terior trees on biological performance of the forest tent caterpillar (Mala cosoma disstria Hbn.). Each year, ten mature sugar maple trees (Acer saccha rum Marsh.) were selected at the forest edge and in the forest interior. Le aves were collected on branches located at 3-6 m above ground at intervals of one or two days. These leaves were immediately brought hack to the labor atory for rearing of insects in Petri dishes (8 larvae/Petri dish) and for chemical analyses. Total nitrogen levels were significantly higher in leave s front edge trees as were nonsignificantly higher levels of soluble sugars and total phenolics and lower water content. Generally, performance of the forest tent caterpillar, except for larval and pupal developmental time, v aried between the forest edge and the forest interior habitats. Pupal weigh t, egg production and pupal survivorship were greater for larvae reared on leaves from edge trees. Stepwise multiple regression analyses revealed that total nitrogen, soluble sugars and water content were closely associated w ith the forest tent caterpillar's performance. These results suggest that f orest edge effects, in terms of leaf nutritional quality, could have import ant implications for forest tent caterpillar populations in sugar maple sta nds.