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Abstract

The daily patterns of reproductive activity in the diamondback moth were studied outdoors in Miyazaki, Japan, between June 1998 and January 1999. Mating primarily began within one or two hours after sunset, although it also occurred during the daytime in the winter. Mating time was longer in cool seasons than in warm seasons. In June to October, oviposition occurred mainly at night with a peak at one or two hours after sunset. In November, however, some eggs were laid during the daytime. Daytime oviposition was observed more frequently in colder seasons. It is suggested that a low nighttime temperature suppresses the normal behavior of the diamondback moth, and changes the nocturnal oviposition pattern to a diurnal one. The daily rhythm of mating behavior coincided most closely with that of egg-laying behavior.