Brachypterizing effect of group rearing, juvenile hormone III and methoprene in the wing-dimorphic cricket, Gryllus rubens

Abstract

The effects of group rearing, topical application of juvenile hormone III, and topical application of methoprene on winglength development were studied in the wing-dimorphic cricket, Gryllus rubens. Group rearing had a strong brachypterizing effect on both an outbred polymorphic stock recently initiated from field-collected crickets and on a laboratory stock nearly pure-breeding for long wings. Transfer experiments demonstrated that group versus individual rearing during at least the first third of nymphal life exerts virtually no influence on the development of long versus short wings. Development could be redirected from long wings to short wings by transferring crickets from individual to group rearing as late as the last stadium. Topical application of juvenile hormone III during both the penultimate and last stadia and methoprene during the penultimate stadium also redirected development from long to short wings. Methoprene applied during the last stadium produced juvenile-adult intermediates. Both the brachypterizing and juvenilizing effect of methoprene occurred at a concentration one to two orders of magnitude lower than the lowest brachypterizing concentration of juvenile hormone. The results suggest that juvenile hormone is a morph-regulating hormone in G. rubens and provide the foundation for future physiological studies of sensitive periods in winglength development.