MORTALITY FACTORS AFFECTING EGGS OF THE FOREST TENT CATERPILLAR, MALACOSOMA DISSTRIA (LEPIDOPTERA: LASIOCAMPIDAE)

Abstract

AbstractParasitism, infertility, and death of fully developed first-stage larvae in eggs (pharate larvae) were the egg mortality factors encountered during a 1967–69 study on the bionomics of the forest tent caterpillar, Malacosoma disstria Hübner, in northern Minnesota. There was no significant difference in the average yearly per cent parasitization and infertility per egg mass; these ranged from 7 to 10% and 1 to 3%, respectively. There was a year to year difference in pharate larval mortality. It ranged from 39% in 1968 to only 9 and 3% for 1967 and 969. Studies showed that egg masses had a tendency to be either nearly complete y hatched or unhatched only in 1968. The variation in pharate larval mortally in these studies suggests qualitative differences in the population. The pharate larval mortality has the potential of influencing population trends of the forest tent caterpillar.