Variation in Forewing Length of the Spotted Cutworm Moth, Xestia c-nigrum LINNÉ, in Northern Japan

Abstract

In the spotted cutworm, Xestia c-nigrum Lint-16, there is found a high positive correlation between the pupal weight and forewing length. This may allow to use the forewing length as an index for the body size. Forewing length was compared among adults collected at different places between about 40° and 43° N. In the bivoltine populations widely found, the overwintering generation had longer wing than the first generation. Within the same generation, average wing length increased from north to south. This clinal change may correspond to geographic gradient in temperature which restricts the duration of growing season. However, there were little differences in wing length among adults from different altitudes at about 40°N, in spite of wide altitudinal variation in temperature. A possible explanation for this might be provided by assuning an altitudinal migration of local scale by adults. The univoltine strain obtained at a highland at 40°N was almost identical in size with the bivoltine ones of overwintering generation from similar latitudes.