Male mosquitoes have a highly developed sense of hearing, though it is much different from that of humans. Male mosquitoes rely on their sense of hearing for breeding purposes. Because of the link between hearing and mating behavior, as well as their impact on human health, the hearing abilities of mosquitoes has been the subject of much study. The limit of mosquito hearing is approximately 2,000 Hertz.
Mosquitoes are equipped with two feathery antennae on their head, and they use these to hear. The antennae are attached at the base to circular structures called Johnston’s organs. Mosquitoes engage in an active, metabolically driven hearing; the antennae filaments are tuned, and adjusted to various frequencies and sound levels. For a long time, females were thought to be deaf, but a 2006 study by Gabriella Gibson and Ian Russell, published in “Current Biology,” demonstrated that females can hear.
The buzzing sound of mosquitoes is caused by the vibration of their wings, and is termed a flight tone. The flight tone of female mosquitoes is about 400 Hertz, and males have hearing that is tuned selectively to the frequency range of 300 to 400 Hertz. When a male perceives a female’s flight tone, he actively pursues her for mating.
Mosquitos have exquisite control over their wings, and by changing the rate they beat their wings, they can change the frequency of the buzzing. The study by Gibson and Russell showed not only that females can hear, but that courting pairs will synchronize their tones. Consistent with the hypothesis that these tones are used in courtship, the frequency of the flight tones of same-sex pairs may converge initially, but ultimately diverges a great deal. In a more recent study by L. J. Cator et al., published in a 2009 issue of “Science.” they demonstrated that one species, Aedes aegypti, was capable of hearing a much wider range of frequencies than previously thought possible. When they analyzed the synchronized tone of courting pairs, it was found to be approximately 1,200 Hertz. The researchers investigated the structure of the hearing apparatus, and found that the cells were responsive to frequencies as high as 2,000 Hertz. Mated females were found to be less responsive to the flight tones of males.
Ultrasonic Mosquito Repellents
Some commercial products exist that claim to repel mosquitoes by emitting ultrasonic sounds. Some radio stations also have tried broadcasting these ultrasonic sounds, thus repelling mosquitoes from their listeners. These sounds often are emitted at 15 kilohertz, which is above the upper limit of sensitivity for most adult humans, so it mostly goes unnoticed. Unfortunately, according to a review of 10 field studies by A. Enayati et al., published in a 2010 issue of “The Cochrane Library,” there is no evidence to suggest these devices repel mosquitoes. Bart Knols, advisory board chairperson for the Dutch Malaria Foundation and entomologist, echoed these findings, adding that there was “no scientific evidence whatsoever” to demonstrating the effectiveness of such devices. Knols went further, adding that mosquitoes aren't even repelled by the frequency produced from dragonfly wings. Predators of mosquitoes, dragonflies produce a flight tone of 20 to 170 Hertz, which is much lower than the tones emitted by ultrasonic repellant devices.
- The Journal of Experimental Biology: Mosquito Hearing: Sound-induced Antennal Vibrations in Male and Female Aedes Aegypti
- Science Blogs: The Harmonic Duets of Mosquitoes in Love
- Current Biology: Flying in Tune -- Sexual Recognition in Mosquitoes
- Proceedings of the National Academy of Sciences of the United States: A Boost For Hearing in Mosquitoes
- Science Daily: Active Hearing Process in Mosquitoes
- BBC: Ultrasound Mosquito Repellents: Zapping the Myth
- The Cochrane Library: Electronic Mosquito Repellents for Preventing Mosquito Bites and Malarial Infection (Review)
- Center for Disease Control: Mosquito-Borne Diseases