Actually, I would like to dedicate this post to the lovely Stephanie Zvan of Almost Diamonds. This is because Stephanie recently sent Sci her blogging muse: an entire box of dark chocolate Moose Munch!!!!!! Moose Munch is indeed Sci’s muse, and could not have come at a better time. Stephanie Zvan is awesome for any number of reasons (I particularly recommend her short stories) , but sending food in the mail definitely adds a little extra.
Unfortunately, this means that last night was spent suffering the effects of a Moose Munch overdose. But today Sci is back up and rolling…literally. And to you, Stephanie, the bringer of my mental muse, I give you…a love song. In major fifths. At 600 and 400 Hz.
Cator et al. “Harmonic convergence in the love songs of the dengue vector mosquito” Science, 2009.
This post brought to you by Stephanie Zvan. And moose munch. Also kilts, rum, and sugar highs.
I’m sure we all know about mosquitoes. I know I cringe at the very sound of that high-pitched whine. If you’re delicious (like Sci), then you KNOW that every time you hear those nasty ear-splitting notes of horror, you can give up, because bug spray or not, you’re going to be scratching for days. But to a lady mosquito, what sounds to us like a teeth-gritting shrill is the hottest love song on the planet.
But we all know that mosquitoes are not just song and itchy bites. They spread many diseases which are endemic in countries around the world, things like malaria, yellow fever, and dengue. These diseases have to have a mosquito as their vector, and so a lot of research has focused on mosquitoes as vectors and how to prevent them getting access to humans (mosquito nets and things).
But for all the research and all the hype we hear about preventing mosquito bites when we go to certain countries, we don’t actually know a lot ABOUT mosquitoes. Ok, we know they come in male and female. Most of the time the female is the one who drinks the blood (though there are some “vegetarian” mosquitoes). We know the females need still water in which to lay their eggs. And…well…yeah. So this paper today is a big deal, not just because it implies a new way in which to possibly fight mosquitoes, but also because it tells us a whole boatload of stuff about them that we never knew before.
So we know they make that high-pitched whine. This is not because mosquitoes are vocally talented, the whine comes from the frequency of wing beats. For males, this is around 600Hz, and for females it’s around 400. This is actually about a fifth apart on the traditional musical scale. The 600 Hz tone is the higher one, which I think might be because the males are smaller, but I’m just guessing there.
One of the things I love about this study was how they did it. First, take a mosquito and tether it to a pin (I would kill to know how they did they, but I’m imagining a very frustrated grad student with very swollen fingers). Leave it free so it can flap its wings. Record the sound into a microphone. Then, hold the boy mosquito near a tethered girl mosquito for a few seconds, moving slowly in and out of range for a few fly-bys. Record the sounds and see what happens.
And what happened? Instead of the male mosquito and female mosquito continuing at 600 and 400 Hz, they made beautiful music together, matching their wing beats to a tone of 1200 Hz. This is a pretty high tone, as you might imagine. Not only that, they could get the bugs to match a mating tone (at 1200 Hz) played artificially, so they could be fooled with a fake. Interestingly, females tended to match a tone only if they were virgins (mosquitoes only make once), and lost interest once they had mated.
So what does this tell us about mosquitoes? Quite a lot. Most scientists believed that mosquitoes could only hear between 300 and 800 Hz, and this tone shattered all the records. Not only that, many researchers believed that only male mosquitoes could hear, and that females were deaf. So males would be able to find females, and females may never know what was coming. But this experiment proves that females can hear, and react to what they hear.
Secondly this experiment could provide a lot of information about how to keep mosquito populations down in heavily populated areas. For example, some people have thought of releasing sterile males into the wild. The males would mate with the female, who would then complete their life cycle and die without ever giving birth. This could significantly reduce the female mosquito population. This experiment backs up this idea, as females are more susceptible to males when they are virgins, so they’d be more likely to mate with the sterile males than if they could just mate loads of times.
The idea that occurred to me was this: bug zappers. Bug zappers make noise, right? It’s not very loud, but all that electricity produces a hum. How much would it hurt to turn it up to 1200 Hz? If the horny mosquitoes can be fooled by a tone, this could encourage them to draw closer and bring some flowers and make dinner reservations, and then…ZAP! Kill them before they mate, and you’ve stopped a major disease vector.
L. J. Cator, B. J. Arthur, L. C. Harrington, R. R. Hoy (2009). Harmonic Convergence in the Love Songs of the Dengue Vector Mosquito Science, 323 (5917), 1077-1079 DOI: 10.1126/science.1166541