Sexual behaviour and pheromone titre in the tomato looper, Plusia chalcites (Esp.) (Lepidoptera: Noctuidae)

Abstract The sexual behaviour of Plusia chalcites (Esp.) was recorded in the laboratory and field. Females reached peak activity on the 4th night between 0.5–2 h into the scotophase. Maximal amounts of pheromone were found in the pheromone glands of 4–5-day old females. Male activity was monitored in a wind tunnel and peak activity was observed with 5–8-day old males, 1–4 h after the onset of the scotophase. Mating occurred 1–2 h after the beginning of the scotophase. In the field, sexual activity of both sexes was synchronized to the first 2 h of night and mating pairs were collected only during the first 3 h, although single females and males were present throughout the night. This timing of sexual behaviour is probably an important factor, in addition to pheromone specificity, in the sexual separation between P. chalcites and other, sympatric, Plusiinae species.