Regulation of juvenile hormone esterase activity in the European corn borer, Ostrinia nubilalis

The regulation of juvenile hormone esterase in last-instar diapause and nondiapause larvae of Ostrinia nubilalis was investigated using topically applied juvenile hormone I and a juvenile hormone mimic, methoprene. The influence of the head on juvenile hormone esterase was also investigated. Both juvenile hormone and methoprene caused increases in esterase levels when applied to feeding animals. Neither the hormone nor methoprene was capable of elevating nondiapause esterase activity to levels comparable to those found in untreated prediapause larvae. The esterase levels could be elevated in the larval body, without the head, during prepupal development of nondiapause larvae and in post-feeding diapause larvae. In both cases, juvenile hormone or methoprene induced juvenile hormone esterase activity in head-ligated animals. Topically applied methoprene prolonged feeding and delayed the onset of diapause. When methoprene was applied to larvae that had entered diapause, it disrupted diapause by inducing a moult.