REARING DENSITY EFFECTS ON PUPAL WEIGHT, WING WIDTH, DEVELOPMENT, ANDFEMALE-ADULT ACTIVITY OF THE FALL ARYMWORM (LEPIDOPTERA, NOCTUIDAE)

Studies of the fall armyworm, Spodoptera frugiperda (J.E. Smith), were undertaken to determine if a high larval rearing density produces pre migrant traits, and if these traits can be used to separate nonpremigr ant 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 fo r separating nonpremigrant from premigrant individuals. Activity of ad ult females was not affected significantly by rearing density. Putativ e morphological premigrant traits were produced by increasing the rear ing density, but developmental and behavioral premigrant traits and be haviors were not. The results of these studies put the existence of a density-dependent premigrant phase in the fall armyworm in question.