Abstract
The gregarious parasitoid Cotesia (= Apanteles ) kariyai (Watanabe) regulates the growth and development of its host Pseudaletia separata (Walker) with the quantity of eggs laid. Fewer parasitoid eggs caused the parasitized hosts to gain less weight. Weight gain of the parasitized hosts is supposed to be correlated with fluctuation of food consumption or food conversion (or both) into body substances. More food consumption and higher efficiency of conversion of digested food into body substance as increasing numbers of eggs laid were not detected. Calyx and venom fluids depressed the weight gain of unparasitized hosts in a way similar to parasitization. However, unlike parasitized hosts, those injected with calyx and venom fluids did not show a rapid decrease in weight after reaching the maximum value. The rapid decrease observed in parasitized larvae seemed to be caused by the developing parasitoid larvae. Female wasps manipulate sex allocation at the time of oviposition to use effectively host resources restricted by calyx and venom fluids. Parasitization of late fifth instar hosts resulted in a more male-biased progeny than that of late third instars. However, an equal number of female progeny was allocated in parasitized late third and late fifth instars, and the number of male progeny shifted proportionally to compensate for the increased number of eggs laid. This suggests that to use effectively the restricted resource of the host without reducing the body size of an individual female (thereby guaranteeing the resource for the development of female eggs), the remaining resource is “assigned” for the development of a suitable number of male eggs, because the size decrease of female progeny is less than that of male progeny in correlation with the number of eggs laid.
Published Version
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