Abstract: As part of a copulation, males transfer ejaculates to the female in internally fertilising species. Ejaculates consist of sperm and glandular secretions referred to as seminal fluid or seminal plasma. In ants, the latter typically consists of at least two distinct parts, a soluble component mixed with sperm and a non-soluble component referred to as a mating plug or a spermatophore. Recent work has provided fascinating examples of the various effects of seminal fluid and sperm on reproductive success. Here I overview our current knowledge about ant copulations and place this information into a broader context of evolutionary biology to exemplify how natural and sexual selection have shaped ant mating systems. Ant copulations have been described for more than 100 species and queen multiple mating is widespread suggesting that postcopulatory sexual selection such as sperm competition or cryptic female choice might be an important selective force in ants. As I point out newly available technologies from the molecular sciences can be used to better understand ejaculate transfer, sperm storage and sperm use, thereby offering exciting opportunities for future work. I here encourage more research into the copulation biology of ants to investigate questions that are of general interest in the fields of evolutionary, reproductive and systems biology.