Sexual behavior of the navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae).

To get a better understanding of the mating behavior of the navel orangeworm, Amyelois transitella (Walker), we developed a robust laboratory colony derived from larvae collected in Bakersfield, California and fed on dried, roasted pistachio. In the lab at 25 degrees C, most of the mating activity was observed during the last hour of the scotophase and for the first 30 min of the photophase. Female calling was characterized by the abdomen being protruded between the wings with the distal segments perpendicular to the body and exposing a pheromone gland, as well as by continuous antennation. Males approached calling females from a short distance by displaying wing fanning and antennation. When a male antennated on a calling female's abdomen, she either accepted the male and lowered the abdomen, or walked away. The accepted male made a final approach parallel to the female's body, but after coupling he rotated 180 masculine with male and female remaining in a linear, abdomen-to-abdomen position for over 3 h in average. In a possible strategy to maximize the chances of mating, the sex ratio was significantly skewed towards males in the first two days of emergence. Almost 80% of mating took place in the first two days after adult emergence, with females mating only once. About 55% of males mated only once and approximately 40% of the observed males mated twice and 5% tree times.