Effects of photoperiod and age on the development of two types of the fat body in the Asian comma butterfly, Polygonia c-aureum (Lepidoptera: Nymphalidae), in relation to adult diapause

Polygonia c-aureum adults of both sexes have two types of fat bodies (small spherical or large long and slender). This butterfly overwinters as adults, and adult diapause is maintained by short day-length (SD) and terminated by long day-length (LD), aging and/or high temperatures. Under SD, both types of fat bodies increased in size with increased adult age until day 40 and then leveled off. Under LD, both fat bodies initially increased but then decreased in size. Since applying JH analog (methoprene) did not affect male fat body development while the accessory glands and simplex developed, we conclude that it was flight behavior, rather than the development of those reproductive organs, that strongly affected the consumption of fat body under virgin conditions. When butterflies of both sexes were kept at 21℃ under SD for 15, 30, or 45 days of adult life and transferred to 5℃ (complete darkness and starved condition), high survival was obtained in butterflies pre-incubated for 30 days. However, in butterflies pre-incubated for 15 or 45 days, survival rates decreased with time under overwintering conditions. The above results suggest that decreasing survival rates in these two treatments were due to insufficient development of the fat body in the former and termination of diapause in the latter. Therefore, we conclude that this butterfly may need sufficient time to develop its fat body to survive overwintering.