Effects of juvenile hormone and rearing density on wing dimorphism and oöcyte development in the brown planthopper, Nilaparvata lugens

Abstract

The brown planthopper, Nilaparvata lugens, shows density-dependent wing dimorphism. By changing the rearing density of different nymphal stages the sensitive periods for wing-form determination were shown to be in the 2nd, 3rd and 4th instars. The 4th (penultimate) instar was most sensitive to a decrease of density which induced brachypterous forms. Juvenile hormones I and II and the analogue methoprene were shown to increase the proportion of brachypters when topically applied to female nymphs near the penultimate instar (0.3 mg live weight). Methoprene was also shown to stimulate vitellogenesis in (presumptive) macropters, which usually initiated the process about 24 h later than brachypters. This effect could be achieved by topical application to either the early final instar nymphs or to the adults 36–48 h after emergence. These results suggest that higher titre of juvenile hormone in the penultimate nymphal instar induces the development of brachypteous wings, and that a high titre in the final nymphal instar and an earlier elevation of the titre in the adult stage cause more rapid development of ovaries in the brachypters.