CHANGES IN THE RESPONSIVENESS DURING 2 PHASES OF DIAPAUSE TERMINATIONIN BRUCHIDIUS-ATROLINEATUS PIC (COLEOPTERA, BRUCHIDAE)

The tropical bruchid Bruchidius atrolineatus (Pie) is in reproductive diapause during the dry season, Previous experiments demonstrated that diapause terminates when beetles are exposed to a short photophase (1 1:13h L:D), a high humidity (70-80% r,h,) and to the presence of pods of the host plant Vigna unguiculata. The structure of the ovarioles ch anges during the course of diapause termination, The previtellogenesis phase corresponds to the beginning of the ovarian maturation process. In the germarium of the ovarioles, the trophocytes initiate secretory activity, and nutritive cords transfer the secretory material into th e oocytes, Despite the presence of vitellogenin in the haemolymph, the growth of the oocytes is minimal, Some females produce a sex pheromon e and exhibit reproductive behaviour, The vitellogenesis phase is char acterized by completion of the ovarian maturation process and marks th e end of diapause termination, The presence of V. unguiculata pods doe s not induce the previtellogenesis phase but stimulates the transition from previtellogenesis to the vitellogenesis phase and allows the pro duction of mature oocytes, The diapause intensity is high at the begin ning of female imaginal life and decreases with age, This decrease in diapause intensity prevents a;premature termination of the diapause at the beginning of the dry season and enables sexual maturation of the females when the conditions are suitable for reproduction and developm ent of their offspring. Copyright (C) 1996 Elsevier Science Ltd