Mosquito sound communication: are male swarms loud enough to attract females?

Given the unsurpassed sound-sensitivity of mosquitoes among arthropods and the sound-source power required for long-range hearing, we investigated the distance over which female mosquitoes detect species-specific cues in the sound of station-keeping mating swarms. A common misunderstanding, that mosquitoes cannot hear at long-range because their hearing organs are particle-velocity receptors, has clouded the fact that particle-velocity is an intrinsic component of sound whatever the distance to the sound source. We exposed free-flying Anopheles coluzzii females to pre-recorded sounds of male An. coluzzii and An. gambiae s.s. swarms over a range of natural sound-levels. Sound-levels tested were related to equivalent distances between the female and the swarm for a given number of males, enabling us to infer distances over which females might hear large male-swarms. We show that females do not respond to swarm sound up to 48 dB SPL and that louder SPLs are not ecologically relevant for a swarm. Considering that swarms are the only mosquito sound-source that would be loud enough to be heard at long-range, we conclude that inter-mosquito acoustic communication is restricted to close-range pair interactions. We also showed that the sensitivity to sound in free-flying males is much enhanced compared to that of tethered ones.