Abstract 1. Male Panorpa scorpionflies offer salivary masses as nuptial gifts during copulation. Previous studies have shown that there is usually a strong correlation between the number or size of salivary masses provided and copulation duration. As a result of constant sperm transfer rates, copulation duration is the most important determinant of male fitness in these species.
2. Differences in copulation durations for gift-giving and non-gift-giving males of the Caucasian scorpionfly Panorpa similis have been shown to be much smaller on average than those observed in other Panorpa species. In this study, we therefore focus on the number of sperm transferred in copulations of P. similis both with and without salivary masses.
3. We find that although the average copulation duration in the presence of nuptial gifts is only twice as long as the average copulation duration without nuptial gifts, gift-giving males transfer almost 11 times more sperm during copulations than non-gift-giving males. This is as a result of substantially higher sperm transfer rates (sperm/minute) in copulations in which nuptial gifts are present.
4. Implications of this finding for the interpretation of the mating system of P. similis and the question of which sex controls sperm transfer rates are discussed.