A mosquito's hum may drive humans crazy, but to other mosquitoes it's love at first buzz. Now, scientists have discovered that the sound frequencies generated by the insects' beating wings help mosquitoes of the opposite sex coordinate a romantic rendezvous.
Finding a mate is tough, especially if your vision isn't very good. Male mosquitoes seem to solve the problem by homing in on the approaching buzz of a potential partner. But how do they tell the guys from the girls? And do females play an active role in this auditory courtship given their smaller and less sensitive antennae?
Those have been tough questions to answer, says Gabriella Gibson, a behavioral entomologist at the University of Greenwich in Kent, United Kingdom, particularly because recording the sounds of flying insects is a logistical nightmare. Still, Gibson's team decided to give it a try. Using a dab of beeswax, the researchers separately tethered a male and female mosquito to small clamps via a thin metal wire. They then set up a tiny microphone near each insect.
When the female was encouraged to fly, a curious symphony ensued. The male let loose with a flurry of rapid wing beats, creating a higher-frequency buzz than that emitted by the female. In response, the female slightly increased her wing beat frequency to try to match the buzz of the male, with the male slowing his hum frequency dramatically to match hers. Within a second, the buzzes of the two insects were in perfect harmony. "They synchronize beautifully," says co-author Ian Russell, a neurobiologist at Sussex University in Brighton, U.K.
In the wild, this synchronicity may help ensure a fruitful courtship. Gibson predicts that if two males are in close proximity, they will have a hard time coordinating their fluctuating buzzes. But a male will have a much easier time synching with an approaching female, because she makes more subtle adjustments. For their part, says Gibson, females target males by listening for sudden changes in frequency; they avoid hooking up with other females by distancing themselves from subtle buzz changes. Indeed, when the researchers tethered two males or two females near each other in the lab, their tones deviated from one another and did not converge, the team reports 11 July in Current Biology.
Auditory communication between male and female mosquitoes is a "totally new" finding, says entomologist Peter Belton of Simon Fraser University in Burnaby, Canada. In the future, he notes, it would be interesting to record the sounds of mosquitoes in the wild to confirm Gibson's hypothesis.