Asymmetric effects of adult nutrition on reproductive success of male and female Diaeretiella rapae (Hymenoptera: Aphidiidae)

The role of diet supplements (honey, water or no supplements) on egg maturation, oviposition strategy and longevity of the parasitic wasp Diaeretiella rapae McIntosh (Hymenoptera: Aphidiidae) is investigated. Parasitoids feed as larvae on hosts to acquire nutrition for growth and development, and further gain additional resources during their adult stage by feeding on either host or nonhost resources. The additional resources acquired by adults can help them to increase their reproductive activity or life expectancy, or both. Diaeretiella rapae females emerge with some developed eggs and no additional resources are required for egg maturation or successful oviposition. Females are able to oviposit and produce viable offspring immediately after emergence, and the number of eggs left in the ovaries of females decreases with subsequent oviposition, suggesting that ovigeny index of D. rapae is inclined towards pro‐ovigenic status. When unmated males and females are offered honey solution, females are attracted to it, whereas males display courtship and make mating attempts but then feed on honey after mating. The oviposition efficiency of female D. rapae increases by 30% when they feed on honey compared with when starved. Honey‐fed D. rapae adults live significantly longer (almost twice as long) than starved adults. Honey‐fed females deprived of hosts live longer than those offered hosts regularly. The positive effects of honey‐feeding on longevity are greater in females than in males. Taken together, the results of the present study suggest that the provision of additional resources to adult D. rapae parasitoids could enhance their life expectancy and parasitism efficiency in biological control programmes.