Abstract
The flight muscles of overwintering adults collected at hibernation sites were poorly developed, but the muscles developed after the adults fed on grasses present in these areas. The ovaries were undeveloped or showed discrete evidence of development. The flight muscles of all the adults which were flying around the hibernation sites had fully developed and the width of the epipleural muscles was 156-216μm. The ovaries were poorly developed and most of them had no mature eggs. After the adults immigrated into paddy fields and fed on rice leaves, their flight muscles began to degenerate, whereas their ovaries developed and had mature eggs. The newly emerged adults, had poorly developed flight muscles just after emergence, but the flight muscles soon developed during the adults stayed in the paddy fields. The flight muscles of all the adults caught into vinyl sheet traps had fully developed and the width of the epipleural muscles was 156-216μm. After the adults moved under fallen leaves at the hibernation sites, their flight muscles started to degenerate. Ovaries of newly emerged adults caught during late July to early August were poorly developed. It is considered that overwintering and newly emerged adults develop full grown flight muscles and are able to show active flight behaviour only during the period of migration.
