The Control Mechanism Of Life Cycle Of A Cockroach, Blattella Germanica

In this paper, the strategies and the control mechanism of life cycle of Blattella germanica are studied, according to the reponse to photoperiods and temperature.Effect of photoperiods on nymphal development of B. germanica. Nymphal diapause is induced by short days(LD 12:12h) at either 30℃, or 20℃. The model for the reponse to photoperiod in B. germanica is long-day reponse. Nymphs grow rapidly under the condition of long days(LD 16:8h) and enter diapause under the condition of short days. Nymphs grow slowly after transferred to LD 12:12h from LD 16:8h, and grow rapidly after transferred to LD 16:8h from LD 12:12h.Effect of photoperiods and temperature on nymphal instars. the number of nymphal instars varied respectively. At 25℃, adults emerge after passing 7 instars at LD 16:8h, 8 instars at LD 14:1 Oh, and 9 instars at LD 12:12h, the number of nymphal instars are increased respectively under the condition of short days, adults emerge after passing 7 instars at 30℃ and 25℃, whereas, adults emerge after passing 9 instars at 20℃.Effect of photoperiods and temperature on reproduction of B. germanica. There is no difference in pre-productive period, time intervals and number of hatching nymphs, when adults of this cockroach reared at different photoperiods and 25℃. This shows that eggs of B. germanica have no diapause, and photoperiods have no effect on hatching of oothecae. On the other hand, the percentage of oothecae development is great at short days than long days. The number of hatching nymphs in a oothecae is the biggest at 25℃ among the three temperature, and the smallest at 30℃, Suggesting that the optimal temperature for reproduction is 25℃, low temperature and high temperature is unfavourable for reproduction.Effect of temperature on the survival of oothecae. Under the condition of short days or long days, the survival of oothecae is greatest at 25℃ among the three temperature, It is 78%( LD 16:8h) and 100%( LD 12:12h) at 25℃, the smallest at 30℃, it is 18% at LD 12:12h and 30℃, what is more, there is no developmental oothecae at LD 16:8h and 30℃. Suggesting that there is a significant effect of temperature on the survival of oothecae.