Effect of Several Temperature Regimes on the Development and Timing of Responsiveness of Males of Trichoplusia ni to the Female Sex Pheromone

Abstract

Males of Trichoplusia ni (Hübner), the cabbage looper moth, were maintained at two constant temperature regimes, 25° and 15°C, as well as at an alternating 25° day:15° night regime. The males held at constant 15° required at least 9 days following emergence from the pupa to acquire maximal responsiveness to the synthetic female sex pheromone, cis -7-dodecenyl acetate, whereas those held at constant 25° or at 25:15° were maximally responsive by 3–5 days following emergence. Within a 10-hr scotophase, males held at 25°, 25:15°, and 15° achieved maximal pheromone responsiveness by the 7th, 3rd, and 1st hours, respectively, after the onset of darkness. This advancing of the diel expression of responsiveness with reducing temperatures is similar to that seen earlier for the time of release of pheromone by T. ni females. Males conditioned at the more natural, fluctuating (25:15°) temperatures tended to be 3 to 6-times more responsive to pheromone than those maintained at the constant (25° or 15°) temperatures.