Observations on the feeding and mating behaviour of Rhamphomyia spp. in the high arctic are reported. In R. nigrita Zetterstedt the males catch their prey especially in the male swarms of mosquitoes, etc., and carry it to their specific swarming (mating) site, a station controlled by a typical visual marker. In the swarm the male responds to insects hovering above, by rising to within a few inches and then holding a steady distance for some moments. The upper insect, if a male, moves away; if a female, pairing soon takes place, the prey is transferred, and the female feeds on it during mating. Apparently the female obtains insect food in no other way. The prey is rather small, and insufficient for the completion of one ovarian cycle; and the swarming flight, with mating and prey transfer, occurs repeatedly.In R. ursinella Melander hunting and mating are accomplished on the ground. The prey is very small and mating is frequent. The species is virtually non-flying, and the specialized form of the male eye, on which mating in flight depends, is considerably reduced. Similar adaptations occur in other arctic Diptera. R. nigrita, in contrast, maintains fully the normal dependence on sustained flight.The general structure of mating behaviour in the specialized Empidinae (Rhamphomyia, Empis, Hilara) is discussed. As in many Empididae, and other Diptera, mating takes place at an assembly station controlled by a visually recognized swarm marker, and the response to the female is mediated by the large ommatidia of the upper part of the male eye. The "holding flight" however signifies an interposed courtship, or display of prey by the male to the female. In most species only the male captures prey (perhaps without feeding on it himself); the female does not hunt and obtains insect food only by transfer at mating. Courtship with transfer becomes a firmly established behavioural element, and persists even in species which use objects of no value as food (ritualization of prey).The original significance of the prey, on which its role as sign stimulus in mating is based, is its significance as food required by the female for ovarian maturation. When the prey is small in relation to the requirements of the female, the mating process, including the courtship and prey transfer, is repeated (ritualized) so as to provide the female with sufficient food. It is suggested that this ritualization would develop easily once insect prey had become established as the sign stimulus for mating; and could lead on to the sex differences in habits of hunting and feeding.