The insect growth regulator NC-184, a juvenile hormone mimic, prevents moulting to the adult stage in the desert locust, Schistocerca gregaria (Forskål) (Orthoptera: Acrididae). Male nymphs treated in the penultimate or final nymphal instar with NC-184 exhibit precocious mating behaviour in the final instar. We examined whether this chemical affects the development of the internal reproductive organs of crowded nymphs. In treated males, both accessory glands and seminal vesicles were underdeveloped, and no sperm was found in the seminal vesicle, whereas these organs in control individuals had greatly increased in size 10 days after treatment, when all the insects had moulted to adults. Testis size in treated males was similar to that in controls, regardless of their smaller body size due to the inhibition of moulting. Oogenesis and development of spermatheca in females treated with NC-184 continued to some degree, but no eggs matured, unlike what occurred in the control. In conclusion, treatment of S. gregaria nymphs with NC-184 resulted in changes in the reproductive organs in both sexes.
Reproduction and wing patterns (shape and colouration) in Polygonia c-aureum L. (Lepidoptera: Nymphalidae) are regulated by both photoperiod and temperature experienced during the immature stages, which result in the development of summer or autumn forms. The critical day length for this seasonal change in form was 13.5L : 10.5D at 21°C and 13L : 11D at 25°C. We investigated the connection between seasonal form and female reproduction. Under a 15L : 9D photoperiod at 21°C, reproductively active summer form butterflies are produced, whereas under an 8L : 16D photoperiod at 21°C autumn form butterflies with a strong tendency to enter diapause were produced. On the other hand, under the critical day lengths at 21 or 25°C, autumn form butterflies developed with a weak tendency to enter diapause. When the adult butterflies were transferred from a critical or a short photoperiod to a long photoperiod shortly after emergence, the former were more likely to terminate diapause than the latter. If individuals are reared throughout their entire life cycle under a short photoperiod at 21°C, all the adults have a strong tendency to enter diapause. These results reveal the quantitative effects of photoperiod on diapause in this butterfly and strongly indicate that the determination of the autumn form and induction and maintenance of diapause are not rigidly coupled, at least under laboratory conditions.