SPERMATOPHORE SIZE AS DETERMINANT OF PATERNITY IN AN ARCTIID MOTH (UTETHEISA ORNATRIX)

Female Utetheisa ornatrix exercise postcopulatory mate selection, favo ring sperm of larger males. Larger males also produce larger spermatop hores, raising the question whether males are selected on the basis of body size or the size of their spermatophore. We here present evidenc e, based on matings in which males were induced to deliver spermatopho res disproportionate in size to body mass, that the determinant is spe rmatophore mass.