Longevity, fecundity, and progeny sex ratio of Pteromalus cerealellae in relation to diet, host provision, and mating

We investigated the effects of diet (sugar feeding), host provision, and mating on the longevity, fecundity, and progeny sex ratio of Pteromalus cerealellae (Ashmead) (Hymenoptera: Pteromalidae), an ectoparasitoid of several stored-product insects. Sugar feeding (25% sucrose solution) increased male lifespan by a factor of 3–4 relative to sugar-starved (provided water only) or completely starved (provided no water and no sugar solution) males, irrespective of mating status or host provision. Sugar feeding also increased longevity of females which were not provided hosts, but had no effect on longevity of females which were provided hosts, suggesting that supplemental sugar feeding is beneficial to females only in the absence of hosts. Females had a significantly greater longevity than males: Mean (± SE) longevity of sugar-fed unmated females provisioned with no hosts (36.3 ± 1.2 days) was significantly greater than mean longevity of sugar-fed unmated males provisioned with no hosts (29.7 ± 0.9 days). A negative effect of mating on longevity was recorded only in the absence of hosts but not when hosts were provided. In general, sugar feeding resulted in a modest increase in progeny production by female P. cerealellae and this was significant for one batch of attacked hosts. However, cumulative lifetime progeny (mean ± SE) of sugar-fed females (64.2 ± 9.2) was not significantly greater than that of sugar-starved (44.5 ± 6.8), or completely starved (54.5 ± 9.3) females. Nevertheless, progeny of sugar-fed females was female-biased (53% females) compared to male-biased progeny recorded for completely-starved females (37% females). These results suggest the potential impact of sugar feeding on survival, fecundity, and sex allocation in P. cerealellae.