Egg load and body size of lab-cultured Cotesia marginiventris

The egg load of lab-cultured Cotesia marginiventris (Cresson) (Hymenoptera: Braconidae), a solitary koinobiont endoparasitoid of noctuid caterpillars, was determined in this study. Information on egg load may provide clues to more efficient in vivo rearing of C. marginiventris. I tested the hypothesis that egg load, defined as the number of mature oocytes (i.e., fully chorionated eggs) found in adult females, was related to body size. Cotesia marginiventris females possessed two ovaries and two ovarioles per ovary; mature eggs were found in ovaries and oviducts. Newly-emerged females held an average of 149 mature eggs. Immature eggs were slightly visible in the distal portions of the ovarioles; they were not counted. Egg load was marginally related to body size (i.e., hind tibia length). The results of this study suggest that (1) body size can sometimes predict egg load or potential fecundity of lab-cultured C. marginiventris and (2) an efficient rearing system that exploits the potential fecundity of C. marginiventris might involve using young females and allowing them to oviposit in new hosts, each day, for up to a week.