Ovarian Development in Predacious Orius pumilio: Relationship to Diet, Mating, and Juvenile Hormone

Abstract

Abstract A female minute pirate bug, Orius pumilio (Champion), was found to require both food and mating as an adult to achieve egg development. Last-instar nymphs of O. pumilio were individually placed into 96-well microtiter plates and recovered 24–48 h later as virgin adults, fed only on sucrose or water. The procedure yielded low mortalities. Correct identification of the sex of individuals as last-instar nymphs was achieved with 96% accuracy. The availability of food (eggs of Ephestia kuehniella Zeller) and mates for these isolated females was controlled. Unfed adult females, whether mated or not, did not produce defectible yolk protein when assayed by enzyme-linked immunosorbent assay, nor did they show any follicle development when examined microscopically. Fed but unmated females produced a significant, defectible amount of yolk protein, and some oocyte development was observed, but they contained no fully mature eggs. Females that were both fed and mated fell into two categories: 44% produced mature eggs at a mean rate of 6.4 eggs per female, whereas 56% had ovaries similar to those of fed but unmated females. If treated in mixed sex groups, females that were fed and mated contained more yolk protein than those held in pairs, but increasing the sex ratio of groups above 0.5 (males:females) did not result in a significant increase in yolk protein content. Topical treatment of fed females with methoprene, a juvenile hormone analog, did not trigger an increase in yolk protein contents. We conclude that vitellogenesis is a two-stage process in adult female O. pumilio. Early vitellogenesis requires a nutritious adult diet, whereas full vitellogenesis and egg maturation also require mating.