In the parasitic wasp Melittobia digitata, sex ratios are extremely female biased, about 95%. Sib-mating occurs within the host puparium, with females mating only once and males mating repeatedly. If a mate is not found, virgin females can produce a small group of male offspring and then mate with a son. The relative frequency of each of these types of reproduction is unknown. Because males are rare, male fecundity plays a critical role in determining if a female will be inseminated.
The objectives of this study were to determine the number of females that an individual male can inseminate and to determine if the sperm contribution per female changes with male age or mating experience.
Newly eclosed males were placed in individual vials with female pupae, allowing mating to occur as females emerged. Females were assumed to have mated when they exhibited positive phototaxis. For the lifespan of each male, mated females were removed twice daily, placed individually on Sarcophaga bullata hosts, and replacement pupae added to the vials. After four weeks, offspring were sexed and counted.
Males lived an average of 7.7 days and each inseminated 163.5 females. Mated females produced an average of 136 offspring. Only 1 or 2 males would be needed to inseminate all of the females on a host of this size. Both the number and percentage of female offspring remained constant with male age and mating experience.
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