An alternative mating system in small male insects

. 1. Small males of all midge (Diptera: Chironomidae and Chaoboridae) species thus far examined (one chaoborid and six chironomids) are rare in mating swarms. They are found instead in vegetation adjacent to the swarm. 2. We show that it is here that females aggregate prior to embarking on mate acquisition flights. In the vegetation females appear to be accessible to males staying behind. 3. Such behaviour in small males may exploit the mate‐attracting activities of large males in the swarm and may, at the same time, reduce competition and conserve energy. 4. The evolution and maintenance of these size‐related types of mating behaviour are discussed.