Long- and short-range bimodal signals mediate mate location and recognition in yellow fever mosquitoes

Mate location and mate selection behavior in diurnally-active yellow fever mosquitoes, Aedes aegypti, take place in mating swarms but the mechanisms underlying swarm formation and long-range detection of females by males remain largely unexplored. In high-speed video recordings we show that incident light reflects off the wings of swarming males, and in behavioral experiments we demonstrate that swarm formation and mate recognition are mediated, in part, by these wingbeat light flashes and by wingbeat sound signals that operate at long and short range, respectively. To test for range-dependent effects of these signals, we presented mating swarms in form of two paired 8-LED assemblies that were fitted with micro-speakers and placed either well separated in a large space or side-by-side in a small space. In the large but not the small space, the LED assembly flashing light at the wingbeat frequency of females (665 Hz), and emitting their wingbeat sound (665 Hz), attracted and prompted 5.8-times more alightings by males than the LED assembly emitting constant light and wingbeat sound. In the small space, the LED assembly flashing light and emitting wingbeat sound induced 5.0-times more alightings by males than the LED assembly flashing light without wingbeat sound. The attractiveness of light flash signals to males increased with increasing numbers of signals but did not vary according to their wavelengths (UV or blue). Females responded to light flash signals of males. As predicted by the sensory drive theory, light flashes had no signal function for crepuscular house mosquitoes, Culex pipiens.