The reproductive biology of Perillus bioculatus

T. S. Adams

USDA-ARS-BRL, 1605 Albrecht Blvd., Fargo, ND 58105-5674, USA

A method is presented to quantitatively score the degree of ovarian maturation in a predacious pentatomid with asynchronous follicle development. Ovarian scores were not influenced by mating status, but were significantly lower in females fed the artificial diet. Ovarian follicles start forming when females are 2.3 days old reaching a peak at 4.5 days. In controls, the rate of new follicle formation decreases after the onset of vitellogenesis. By 4.5 days, all control ovarioles contained at least one vitellogenic follicle and by 9.5 days all ovarioles had chorionated follicles. In contrast, females fed the artificial diet had 40% of the ovarioles with a vitellogenic and chorionated follicle at 10.5 days of age. Mating started when females were 3.5 days old and correlated with the start of vitellogenesis. Mating and an adequate diet are prerequisites for laying a full compliment of eggs in Perillus bioculatus. Virgins laid an average of 22 eggs compared with 138 in the multiply mated controls and 84 in singly mated females. Multiply mated females given an artificial diet only laid 42 eggs. Oviposition rates were calculated over five-d periods for each female and presented as eggs/ovariole/d (eod). In all experimental groups the rates of egg laying decreased as the females aged approaching 0.07eod by 27.5 d after the start of oviposition. Two factors affecting egg laying are: 1). Availability of mature ovarian follicles in the ovariole and 2). Mating. Unmated females develop mature ovarian follicles, but do not oviposit many of them. Mated females given the artificial diet develop fewer mature ovarian follicles, but oviposit them. Hemolymph vitellogenin titers were determined with an ELISA technique. Insects given the artificial diet had lower vitellogenin levels than those given prey. The interaction of diet with hormones required for ovarian maturation will be discussed.

Index terms: Perillus bioculatus, fecundity, artificial diet, oviposition rate, vitellogenin.

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