抄録
When larvae of the Akita strain (bivoltine, 39°N) of Chlorops oryzae MATSUMURA were reared on rice-plant seedlings younger than the 4 leaf stage under LD12:12 or 14:10, most pupated 25 days after hatching. Under long day conditions (LD15:9), by contrast, most larvae failed to pupate and remained in the first or second larval stage 25 days after hatching when reared on 7-leaf-stage seedlings. On the other hand, larvae of the Aichi strain (trivoltine, 35°N) reared on rice seedlings of the 5 leaf stage or younger grew fast under both short and long days. Larval development was delayed under an intermediate day (LD14:100. This suppression of larval development in the Aichi strain became more marked as the rice plants aged. These results suggest that larval development in the first generation of the bivoltine strain and the second generation of the trivoltine strain is retarded by photoperiodic and host-plant conditions. This retarded development in the early larval stage may be regarded as diapause mediated by food plant and photoperiod.
