Sex Pheromones of Noctuid Moths. V. Circadian Rhythm of Pheromone-Responsiveness in Males of Autographa californica, Heliothis virescens, Spodoptera exigua, and Trichoplusia ni (Lepidoptera: Noctuidae)12

Males of the alfalfa looper, Autographa californica (Speyer); tohacco budworm, Heliothis virescens (F.) ; beet armyworm, Spodoptera exigua (Hübner); and cabbage looper, Trichoplusia ni (Hübner) exhibited a cyclic rhythm of responsiveness to the sex pheromones extracted from females of their respective species. When the males were synchronized to a 12:12-hour light :dark cycle, maximum pheromone-responsiveness occurred during the hours of darkness. The response rhythms were maintained for at least 36 hours under conditions of continuous darkness. In T. ni, a reversal in the 12:12-hour light:dark cycle was followed by a complete reentrainment of the male responsiveness rhythm to the new cycle within 24 hours. A 24-hour rhythm of responsiveness could be synchronized in T. ni males by light:dark cycles as abnormal as 20:4 or 4:20. However, the time of maximum responsiveness did not appear to be related in a constant manner to the time of initiation of light or darkness.