Accumulating behavioural data indicate that aggregation
pheromones may mediate the formation and maintenance of mosquito swarms. However, chemical cues possibly luring mosquitoes to swarms have not been adequately investigated, and the likely molecular incitants of these complex reproductive behaviours remain unknown. Here we show that males of the important
malaria vector species Anopheles arabiensis and An. gambiae produce and release aggregation
pheromones that attract individuals to the swarm and enhance mating success. We found that males of both species released significantly higher amounts of
3-hydroxy-2-butanone (
acetoin),
6-methyl-5-hepten-2-one (
sulcatone),
octanal,
nonanal and
decanal during swarming in the laboratory. Feeding males with stable-
isotope-labelled
glucose revealed that the males produced these five compounds. A blend composed of synthetic analogues to these swarming odours proved highly attractive to virgin males and females of both species under laboratory conditions and substantially increased mating in five African
malaria vectors (An. gambiae, An. coluzzii, An. arabiensis, An. merus and An. funestus) in semi-field experiments. Our results not only narrow a conspicuous gap in understanding a vital aspect of the chemical ecology of male mosquitoes but also demonstrate fundamental roles of rhythmic and metabolic genes in the physiology and behavioural regulation of these vectors. These identified aggregation
pheromones have great potential for exploitation against these highly dangerous insects. Manipulating such
pheromones could increase the efficacy of
malaria-vector control programmes.