Flies with Ulidiid have a very strange habit: after mating, it releases male sperm and eats. Their strange behavior allows flies to choose their fathers for their children.
A recent study of Euxesta bilimeki showed that all 74 flies they studied had sperm secretion after mating. 25% of them do not have any sperm in them. Scientists believe that the fly can regulate the number of spermatozoa that can be used to choose the father's fly for their children.
There is also a theory that male sperm can provide nutrients to the female. To test this hypothesis, the researchers fed flies with food containing protein, sugar and water: sugar and water, no water and no food. They then gave these females to the side of the males capable of launching sperm and unable to ejaculate.
The results showed that flies who ate enough nutrients or only drank water did not benefit from sperm. However, flies that do not eat can live longer if they eat sperm.
However, for many species, females do not receive nutrition from sperm. Maybe sperm eating habits are part of their mating efforts.