Rearing Density EfiFects on Pupal Weight, Wing Width, Development, and Female Adult Activity of the Fall Armyworm (Lepidoptera: Noctuidae)

Abstract

Studies of the fall armyworm, Spodoptera frugiperda (J. E. Smith), were undertaken to determine if a high larval rearing density produces premigrant traits, and if these traits can be used to separate nonpremigrant from premigrant individuals. An increase in larval rearing density significantly decreased pupal weight and forewing width in three out of five experiments. Developmental time was not a definitive factor for separating nonpremigrant from premigrant individuals. Activity of adult females was not affected significantly by rearing density. Putative morphological premigrant traits were produced by increasing the rearing density, but developmental and behavioral premigrant traits and behaviors were not. The results of these studies put the existence of a density-dependent premigrant phase in the fall armyworm in question.