Effects of Photoperiod on Nymphal Growth of Palomena angulosa MOTSCHULSKY (Hemiptera : Pentatomidae)

Total mortality during the nymphal stage of Palomena angulosa MOTSCHULSKY extended from 14% to 48% in groups subjected to natural day-length (N-groups), while it ranged from 36% to 64% in groups exposed to stationary long-day (16L-8D), significantly higher than that of their N-group counterparts. In N-groups, the nymphs grew more quickly when put under shorter photophase condition. Stationary long-day photoperiodic condition retarded the nymphal growth (L-groups). In N-groups, daily weight gain in the nymphal stage tended to be greater when the nymphs were exposed to shorter photophase. Compared with respective counterparts of N-groups, the weight gain in all L-groups was significantly less in the 4th and 5th instars. Adult weight did not differ among the groups, except the group fed sucrose in the 2nd instar in the N-group (significantly lighter). P. angulosa was of a short-day type or a decreasing photoperiodic type in relation to nymphal growth. The significance of these results is discussed in relation to the history of P. angulosa.