Utetheisa ornatrix females mate with many different males, but only one their mates generally sires the progeny. To investigate the mechanism of this sperm precedence, we counted the sperm contained within the spermathecae of field-caught females. Captured females contained the remains of between 1 and 23 spermatophores, each received at a separate mating. Females that contained one spermatophore had an average of 2,760 fertilizing, or eupyrene, sperm within their spermathecae. The number of sperm within twice-mated females decreased to 1,600, and the greatest number of sperm was found in females containing between 3 and 8 spermatophores, although the number varied between 0 and 30,000. These data suggest that sperm may be lost from the spermatheca, and that it may never arrive there after some matings. These moths also produce non-fertilizing, or apyrene, sperm, which were present in great tangles, making them impossible to count. The tangles suggest a blocking function for the apyrene sperm.
Species 1: Lepidoptera Arctiidae Utetheisa ornatrix
Keywords: sperm competition, sperm storage
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