Abstract
Although Carbula humerigera may enter diapause and overwinter at the nymphal stage in response to a short photoperiod, it is still sensitive to photoperiod at the adult stage. At 25°C, the females laid eggs in a long photoperiod (14 hr or longer) but not in a short one (13.5 hr or shorter). At 20°C, the critical daylength is longer than that at 25°C, being between 14L-10D and 15L-9D. In spite of this long-day type response to stationary photoperiods, an increase in photoperiod from 14L-10D to 16L-8D at the 5th instar suppressed oviposition and a decrease from 16L-8D to 14L-10D at the adult stage promoted it. A similar retarding effect of increasing photoperiod was exerted by a transfer from 12L-12D to 14L-10D, but not by a transfer from 15L-9D to 16L-8D. The life cycle of this species thus seems to be stabilized by the combination of the different nymphal and adult photoperiodic responses.
