Flight activity of three Spodoptera spp., Spodoptera litura, S. exigua and S. depravata, measured by flight actograph

Flight activities of three Spodoptera species were measured by the aid of flight actograph: S. litura and S. exuiga being regarded as long‐distance migratory insects, and S. depravata being non‐migratory and diapause‐inducible species. In all species tested, flight activities were observed only in scotophase, males showed far higher activities than females, being several times higher at the time of maximum flight activity, which was observed within 2 days after adult eclosion. Total flight activity in males was highest in S. litura, some being flyable even 12 days after eclosion, followed by S. exigua being one‐third compared to the former species, while in S. depravata flight activity was nearly half of that of the second species and most ceased to fly within a week after eclosion. There occurred species‐specific daily rhythms in flight activity during respective scotophase. In S. litura, both females and males exhibited a peak of flight activity shortly after light‐off and exhibited the second flight activity in late scotophase, the females slightly but the males more actively compared to early scotophase. In S. exigua, both sexes did not respond to light‐off, did not show a peak of flight activity in early scotophase, whereas males, but not females prominently increased activity toward the end of scotophase. In S. depravata, both sexes exhibited a peak of flight activity in early scotophase, and the males revived flight activity, being maximum shortly before light‐on, but the females did not show a clear rhythm in flight activity. These features observed in flight activity were discussed in relation with migratory capability.