Abstract
Seasonal occurrence of Spodoptera litura (F.) was studied with a virgin female trap in Chikugo from 1972 to 1975. Catches in a water trap baited with 10 1-day-old females were counted daily from mid-March to mid-December, and the number of egg masses laid on taro plants in the field was counted twice weekly from June to November. Spring emergence started between late March and early April and flight activity lasted until mid-December, during which five generations were detected and the number of captured moths increased as the season progressed. The virgin female trap caught 81 times more male moths than did a light trap equipped with a 20-watt fluorescent chemical lamp (BLB) and the seasonal incidence of moth capture differed considerably between the two traps: namely, in the virgin female trap four peaks were detected during June to October, whereas no similar trend was obtained in the light trap. The virgin female trap seemed to be more effective in the early season when field populations were low. Egg masses were found on taro plants from July to early November. During this period the largest ovipositional peak, that of laying by the third generation moths, was usually found between late August and early September. In the third generation, the date of 50% oviposition was 4 to 10 days earlier than that of 50% moth capture by the virgin female trap. The number of egg masses laid on taro plants by the fourth-generation moths in October was generally low in comparison with the number of catches by the virgin female trap, owing to the decline of air temperature.
