A study of the phases of the army worm (Laphygma exempta Walk.)

Abstract

Studies made on swarming locusts have shown that there is a number of morphological and developmental differences between hoppers reared in crowds and those reared in isolation. The most striking of these differences is found in the colour pattern, and it is most conspicuous in the final instar hoppers. The hopper reared in a dense crowd has a basic black background colour with orange-yellow markings. The adults are characterized by having longer wings and shorter or more compressed pronota. The isolated forms show a greater variation in the colour pattern of the hoppers, which varies from green to grey-blackish, but the black and orange pattern of the swarm type is never found. The adults of these solitary forms generally have relatively short wings and the pronotum, especially in Locusta migratoria, is larger and much more convex in the lateral aspect.