PHYSIOLOGICAL ECOLOGY Development and Reproduction of the Egg Parasitoid, Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae), as a Function of Temperature

Thedevelopment, fecundity, and life tableparameters ofGonatocerus ashmeadiGirault, an egg parasitoid of the glassy-winged sharpshooter,Homalodisca coagulata (Say), were studied in the laboratory at six constant temperatures between 12 and 32 C. At 12 C, the parasitoid failed to develop beyond the third instar, and durations of the egg stage and the Þrst and second instarswere prolonged. Development from the egg stage to adult emergence varied from 27.1 d at 16 C to 9.5 d at 28 C. Temperature thresholds for development ranged from 3.8 C for Þrst-instar larvae to 12.8 C for the pupal stage. The thermal constants were lowest for the second-instar larvae (26.7 DD) and highest for thepupae(75.4DD).Nearly207DDwere requiredabove the lower temperature thresholdof8.5 C to complete development from egg to adult. The optimum temperature for egg to adult development was 29.2 C. Survival from egg to adult was 67.4% at 16 C and ranged from 83.4 to 86.7% between 20 and 32 C. At 16Ð32 C, the population had a type I survivorship pattern. At 16 C, longevity of adult females and males averaged 27.1 and 19.0 d, respectively, but declined to 6.4 and 6.9 d at 32 C. At 20Ð32 C, peak adult emergence occurred on the Þrst day of emergence, but at 16 C, it was greatest on the second day. When exposed to temperatures ranging from 16 to 32 C, the female:male sex ratio was similar, ranging from 3.4 to 5.6. Lifetime fecundity was greatest at 24 C and lowest at 32 C, with the maximum net reproduction also occurring at 24 C. Greatest intrinsic and Þnite rates of increase, shortest population doubling time, and mean generation time occurred when G. ashmeadi was held at 28 C.TheparametersdeÞned in this studycan inßuencegeographical distributionandare important for the mass-rearing this wasp as biological control agent for the glassy-winged sharpshooter.