In the laboratory, the timing of both preßight and ßight behaviors of the Asian strain of female gypsy moths, Lymantria dispar L., was regulated primarily by light intensity. The shortest times to initiation of wing fanning and ßight occurred at 0.1 lux, the lowest light intensity evaluated. A gradual decrease in light intensity, compared with an instantaneous decrease, prolonged time to ßight. The highest percentage of female ßight was observed at 0.1 lux. A higher percentage of females

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... ed ßight when exposed to lower light intensities after the onset of normal scotophase rather than before scotophase. Virgin females were less likely to ßy than mated females. Females fanned their wings longer at lower temperatures and when they were capable of only a gliding ßight. Females that were ßight-tested the same day they emerged tended to take longer to initiate ßight than those 1Ð2 d old. At 0.1 lux, the majority of the Asian females, less than 2% of the F 1 hybrid females, and none of the North American females exhibited strong, directed ßight. Over half of the F 1 hybrids glided for a few meters while ßapping their wings, whereas none of the North American females exhibited even this level of ßight. Thus, female ßight capability will be reduced when ßighted and nonßighted forms initially hybridize.