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

Abstract

Fragmentation of forests has considerably increased the amount of edge habitats. This edge effect could have a direct influence on the dynamics of forest 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 interior trees on biological performance of the forest tent caterpillar (Malacosoma disstria Hbn.). Each year, ten mature sugar maple trees (Acer saccharum Marsh.) were selected at the forest edge and in the forest interior. Leaves were collected on branches located at 3-6 m above ground at intervals of one or two days. These leaves were immediately brought back to the laboratory for rearing of insects in Petri dishes (8 larvae/Petri dish) and for chemical analyses. Total nitrogen levels were significantly higher in leaves from 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, varied between the forest edge and the forest interior habitats. Pupal weight, 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 with the forest tent caterpillar’s performance. These results suggest that forest edge effects, in terms of leaf nutritional quality, could have important implications for forest tent caterpillar populations in sugar maple stands.