Changes in mechanical properties of the cuticle and lipid accumulation in relation to adult diapause in the bean bug, Riptortus clavatus

Photoperiodically controlled adult diapause in the bean bug, Riptortus clav atus (Thunberg) (Heteroptera: Alydidae) was due to suppression of corpus al latum activity under short-day conditions. The mechanical extensibility of the cuticle of the pronotum was significantly higher in nondiapause adults reared under long-day conditions than in diapause adults reared under short -day conditions. Furthermore, diapause adults accumulated significantly lar ger amount of lipids than nondiapause ones. It was then examined whether th ese two characteristics of adult diapause also depend on activity of the co rpus allatum, by removal of the corpus allatum and transection of the nervi corporis allati. Even after these two kinds of surgery, adults responded t o photoperiod and showed similar differences both in mechanical properties of the cuticle and in lipid content between long-day and short-day conditio ns. Therefore, inactivity of the corpus allatum is not responsible for the stiffer cuticle or higher lipid accumulation in diapause adults. (C) 1999 E lsevier Science Ltd. All rights reserved.