Curril, Ingrid M.

Utetheisa ornatrix females mate with many different males, but only one of their mates generally sires the progeny. To investigate the mechanism of this sperm precedence, the sperm contained within the spermatheca of field-caught females was counted. Captured females contained the remains of between 1 and 23 spermatophores, each received at a separate mating. The sperm number did not depend on the number of matings. These data suggests that sperm may be lost from the spermatheca, and that it may never arrive there after some matings. In addition to this investigation, a study on the pattern of arrangement within the spermatheca of Utetheisa ornatrix was conducted. Sperm in the spermatheca from multiple and single mated females was fixed and DNA-labeled, and the distribution of eupyrene sperm assessed. The eupyrene sperm distribution did not vary across the sperm mass or with the mating history of the female. Further investigation is required to analyze the distribution of the apyrene sperm tangles within the spermatheca whose function could signify a blocking mechanism against rival sperm.