VOA常速英语:Research on Mosquito Mating Behavior Provides New Insight in Fight Against Disease

Mosquito-borne diseases like malaria, yellow fever and dengue afflict hundreds of millions of people each year. Researchers studying the mating behavior of mosquitoes have made a discovery that may one day reduce the ability of these insects to spread disease. 

Their finding? It's all about the buzz.

It's an unfortunately familiar sound to many of us: the annoying buzz of a mosquito. Female mosquitoes are the worst offenders - they're the ones that bite and transmit disease.

Graduate student Lauren Cator and her colleagues at Cornell University have been studying the mating behavior of Aedes aegypti, the species that transmits yellow fever and dengue.

Mosquitoes use sound to find mates

Remember that annoying buzz? That's the sound the female makes when she's beating her wings together.

"We've known for a very long time that male mosquitoes are able to zero-in on the sound of females from their species," says Cator, in order to find a potential mate.

The male mosquito also buzzes. But his "flight tone," as it's called, is a little higher than the female's.

Previously, British researchers studying another mosquito - a species that doesn't bite people or transmit disease - found that males and females actually change their flight tones to match up with one another, buzzing in unison before mating. Cator wanted to find out whether the disease-carrying Aedes aegypti mosquitoes do the same thing.

But to be able to do that, Cator had to find a way to get a tiny microphone close enough to record a would-be mosquito couple, while they were buzzing around, in flight.

"To do this, I blunted the end of an insect pin, and I attached it using superglue to the mosquito," she says.

She then used "micromanipulators" - little devices with alligator clips on the end - to move the mosquitoes back and forth while they were in flight, so that she could control their interaction.

Tone may indicate partner's suitability

OK... so after gluing the mosquitoes to pins and choreographing their movements, what did Cator actually hear when she brought the males and females together?

As Cator puts it, "It's a little complicated."

To start with, when a mosquito beats its wings, it's actually producing several different tones - or frequencies - at the same time.

There's a fundamental frequency - that's the loud buzzing sound that we hear.

"For a female, that's about 400 hertz, and for a male, that's about 600 hertz," describes Cator.

But at the same time, mosquitoes also produce a series of softer, higher tones called harmonics. Cator and her colleagues found that when they brought males and females together, they changed their flight tones to match up at the female's third harmonic and at the male's second harmonic, at 1200 hertz.

What does all this mean? Cator's research suggests that mosquitoes are using tone-matching as a way of assessing potential mates.

"So how a male synchs, or his ability to synchronize with the female," Cator explains, "may reflect some sort of information about his quality to the female."

Knowledge of mating behavior could help control mosquito-borne disease

Cator says this new understanding of how mosquitoes communicate could be used against the insects.

Researchers are currently exploring ways to control mosquito populations using sterilized males. Releasing these altered males into the natural population to mate could reduce reproduction rates and slow the spread of mosquito-borne diseases.

But such a strategy can only work if the females find the sterile males more attractive than their natural counterparts.

"The problem is we have no idea what constitutes a sexy male mosquito," says Cator.

But, by adding to our understanding of mosquitoes' mating behavior, Cator hopes her research can help contribute to the development of more effective mosquito control programs. Her findings are published in the journal Science.

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