Effect of diet and mating on oviposition in the twospotted stink bug Perillus bioculatus (F.) (Heteroptera: Pentatomidae)

Control females of the twospotted stink bug, Perillus bioculatus (F.), and those given an artificial diet mated repeatedly over their lifetimes when held with males. The average number of observed matings was 4 and 8.4 in the controls and those given the artificial diet, respectively. Mating and an adequate diet are prerequisites for laying a full compliment of eggs in this insect. Virgins laid an average of 22 eggs compared with 138 in the multiply mated controls, 84 in singly mated females and 42 in multiply mated females given an artificial diet. The number of clutches deposited was not significantly affected by treatment, but the number of eggs per clutch was significantly lower in virgins and those given the artificial diet than in the controls or once mated females. The number of eggs per clutch showed no significant changes as the female aged. Oviposition rates were calculated over 5-d periods for each female and presented as eggs per day. In all experimental groups the number of eggs deposited per interval decreased as the females aged. By 27.5 d after the start of oviposition, females from all treatments laid one or fewer eggs per day. The decrease in eggs per day deposited by females as they aged is attributed to an increase in the time between clutch deposition. Egg viability showed no significant differences among the multiply mated controls, once mated females, or the multiply mated females given the artificial diet. This suggests that multiple mating is not required to maintain egg viability, but is necessary to maintain oviposition over the lifetime of the female. Low numbers of eggs oviposited by females given the artificial diet is attributed to the production of fewer mature follicles than in the controls and not to an impairment of the process of oviposition. In contrast, the lower number of eggs laid by virgin females results from an impairment of the oviposition process and not the impairment of ovarian follicle maturation.