Oviposition Rhythm in Crambus teterrellus:1 Temperature-Depression Effects and Apparent Circadian Periodicity2

Abstract

Records of seasonal outdoor oviposition were obtained from females of the bluegrass webworm, Crambus teterrellus (Zincken), paired with males, both sexes being known age. Volume of diel oviposition decreased in September. In late July females oviposited significantly at very low light intensities after exposure to a temperature drop of <1°C in the previous 0.5 hr. In September oviposition began under much higher light intensities after a comparable exposure to a greater (about 3°C) temperature drop. In the laboratory moths oviposited in bright light during a 0.5-hr temperature depression from 25 to 20° C, but not during sudden light intensity change from about 2000 to 230 at 25°C. Amount of evening oviposition stimulated temperature depression compared favorably with stimulated by light-dark transitions. However early afternoon temperature depressions were less effective stimuli. Continued light inhibited oviposition following initial stimulation by temperature depressions. A possible circadian oviposition rhythm was observed, in contrast with earlier findings involving unpaired females unknown ages.