MALE INVESTMENT IN THE EUROPEAN CORN-BORER, OSTRINIA-NUBILALIS (LEPIDOPTERA, PYRALIDAE) - IMPACT ON FEMALE LONGEVITY AND REPRODUCTIVE-PERFORMANCE

1. It is generally assumed that the cost of producing ejaculates is relatively low for males, although the decline observed in spermatophore size with repeated mating in certain lepidopteran species would suggest that this is not always the case. However, despite such observed differences in spermatophores very little research has been done to determine if female reproductive success is affected by the previous mating history of her mate. 2. A study was undertaken, using the European corn borer, Ostrinia nubilalis, to determine the extent to which (i) male lifetime reproductive success was related to the number of mates, acquired and the actual number of times that a male mated when provided virgin females daily for a period of 10 days, (ii) spermatophore size changed with successive matings and (iii) previous male mating history affected the longevity and the reproductive performance of singly mated females. 3. Males mated 3.8 +/- 0.5 times, with a refractory period of 1.6 +/- 0.1 days between mating, and their lifetime reproductive output increased directly with the number of mates acquired. 4. The volume of the first spermatophore produced was correlated to male pupal weight. Spermatophore volume decreased exponentially with subsequent matings, although the difference in volume between the first and second spermatophore was affected by the time elapsed between matings. While the decrease in spermatophore size had no effect on female longevity, pre-oviposition or oviposition periods or the daily pattern of egg fertility, there was a linear decline in both lifetime fecundity and fertility of successive mates of a given male. Furthermore, females mating with males that had previously mated at least three times retained a significant portion of their egg complement. 5. These results suggest that the production of sperm, as well as male accessory gland secretions, may limit O. nubilalis male reproductive output. These findings are discussed with respect to the potential effect that this may have on mate choice in this species.