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Mosquitoes

A porch swing on a summer evening: The hinges creak, crickets trill from the field, the wind sighs gently. Gradually, you become conscious of a vaguely annoying sensation. At first the high-pitched whine barely registers, but it grows louder and closer. Suddenly the whine appears right in your ear. To you the sound communicates only irritation, like fingernails on a chalkboard. But to the male mosquito, it’s a beautiful song, the sound of a female mosquito looking for an evening meal of blood.

Male mosquitoes hear and obey the siren call of the female, flying directly toward the sound—or even a reasonable facsimile. “In fact, you can even attract males with a tuning fork of the proper frequency,” says Marc J. Klowden, a mosquito behaviorist at the University of Idaho. Because the sound comes from the female’s beating wings—mosquitoes cannot vary their wingbeat frequency at will—it rises in pitch as the air temperature rises. Male mosquitoes detects sound not with ears, but with their antennae, which resonate only at the particular frequency emitted by the female. “The male mosquito antenna is built like a tiny tree sitting on a very small joystick; the branches pick up the vibrations and cause the underlying joystick to move. Movement of the ‘joystick,’ called Johnston's organ, is translated into nervous impulses by sensory receptors,” Klowden explains. The impulses signal the male mosquito’s brain, which interprets the sensation as sound. Fortunately for mosquitoes, the resonant frequency of the male’s antennae also rises with temperature, remaining locked in on the pitch of a female of his species. Despite the mechanical relationship between the female’s signal and the male’s response, this communication servers its purpose admirably, producing plenty of mosquitoes—many more than we humans would like.

Next: Crickets