Publication Date


Document Type


First Advisor

King, Bethia H.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences


Muscidifurax raptor; Wasps; Sex ratio; Host-parasite relationships


The effects of host size and female wasp density on offspring sex ratio were examined in the solitary parasitoid wasp Muscidifurax raptor. The prediction of the host-size model that females should produce a greater proportion of daughters from large hosts than from small hosts was supported. The relationship was shown to be a result of maternal manipulation of offspring sex ratio in response to host size rather than a result of differential mortality of the sexes. The assumption of the model that host size has a more positive effect on the reproductive success of daughters than of sons was not supported. Host size did not have a positive effect on the size of either male or female JL raptor, and did not affect male or female longevity, the number of offspring produced by a female, or the number of females inseminated by a male. Host size may differentially affect the reproductive success of male and female wasps through effects on other aspects of reproductive success that were not examined in this study. The effect of the presence of a conspecific female on offspring sex ratio was also examined in FL. raptor. Females forced to oviposit in the presence of another female did not increase the proportion of sons they produced relative to solitary females, contrary to the prediction of local mate competition theory. A possible explanation as to why JL. raptor females did not alter their sex ratio in response to the presence of a conspecific female is that females may have been unable to detect one another.


Includes bibliographical references (pages [55]-60)


viii, 60 pages




Northern Illinois University

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