The northward migration of Helicoverpa armigera (Hübner) and other moths in early summer was observed with radar in 2001 and 2002 at Langfang, Hebei province, China. Migratory flights typically occurred at heights up to 1.2 km above ground level (AGL), and high density layer concentrations frequently formed at 200–300 m AGL. Adult moths of local populations took off at dusk and ceased flight ≈0.5 h before sunrise with area density peaking ≈35 min after dusk. A strong dumb-bell pattern of echoes on the plan position indicator screen, indicating collective orientation of the targets, was evident in 2001, when targets were typically moving toward the northeast and when layering was associated with a temperature inversion and maximum wind speed. By contrast, there was no notable dumb-bell pattern in 2002, when targets were moving toward the northwest. However, orientations calculated from target and wind velocities showed that downwind common orientation also was occurring in 2002 and that the direction varied with the wind direction. The probable sources of the H. armigera observed at Langfang were deduced to be Henan province in 2001 and Shandong province in 2002, and the destination regions were Liaoning and Inner Mongolia.
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Vol. 97 • No. 6