SEASONAL-CHANGES AND EFFECTS OF TEMPERATURE ON FLIGHT ABILITY OF THE DIAMONDBACK MOTH, PLUTELLA-XYLOSTELLA (L) (LEPIDOPTERA, YPONOMEUTIDAE)

Seasonal changes in the forewing length and flight ability of Plutella xylostella were examined for female and male adult moths collected from a cabbage field in Mie Prefecture in 1988. Flight ability was measured by a flight mill. Flight duration and flight distance were longer in winter and spring than in summer. Flight velocity and proportion of moths with long-time consecutive flight did not show a distinct seasonal change. Flight duration and flight distance showed a significant correlation with forewing length; the larger moths in winter and spring had a higher capacity for long distance flight than the smaller moths in summer. In the same months, the flight ability of female moths was almost equal to that of males. The optimum temperature suitable for flight activity of male moths was estimated at ca. 23-degrees-C, with a range from 18 to 28-degrees-C.