The seasonal occurrence of brown-winged green bug, Plutia stali SCOTT was investigated by light traps and pheromone traps for one season in Mino region of Gifu prefecture. To examine the seasonal fluctuation of mean body size, trapped bugs were measured in pronotum size and categorized in five size classes. The ratio of each size class fluctuated, and the proportion of relatively large classes increased in August for both traps. The mean body size of captured bugs decreased from September. Mean sex ratio of the captured bugs was investigated for each month to compare the attractive effect of traps. The ratio of female bugs was fluctuated and increased at the peak period of the number of bugs captured in each trap.
Katsumi Kamiya (Sun,) studied this question.