Abstract & Overview
External conditions such as lack of food and the consequent population density control the swarming of the migratory locust. The transformation is of metabolism and larval development as well as of behaviour. The proportions of body parts and the pigmentation change. As insect development is regulated by juvenile hormone and moulting hormone, there was also the possibility that they were involved in phase polymorphism.The possibility of endocrine control was studied in some types of migratory locust by removing or implanting glands, by cutting nerves and by rearing under different conditions. For the surgical studies a technique was developed for routine operations on large numbers of second-instar larvae and for rapidly measuring the volume of endocrine glands. The green pigmentation of the solitary and the yellow of the gregarious imago was controlled by the juvenile hormone. Body proportions were also thus controlled independent of metamorphic regulation. Moulting hormone had a spectacular effect on development, moulting and body proportions. The studies may be of use in locust control with insect hormones.