10 May 2019

Mosquitoes Interrupted

Welcome back. If there were any doubt, last summer confirmed that Wisconsin’s state bird is indeed the mosquito. To make life worse, the weather was such that Vicki and I finally broke down and installed a window air conditioner. The invading mosquitoes might have slipped through our doorway; more likely, we failed to seal the opening around the air conditioner.

I have never encountered so many mosquitoes buzzing about in a domicile. The hungry females were biting day and night.

Adult female Aedes (Stegomyia) aegypti (yellow fever) mosquito—not our biting invader, but the same structure (from www.researchgate.net/figure/FIGURE-B-Dorsal-view-of-adult-female-mosquito-Aedes-Stegomyia-aegypti_fig32_228820694).
Though I fought valiantly with a hand vacuum, we eventually discovered that the mosquitoes thinned out and slowed down when the air conditioner was actually running. At the time, I attributed their retreat and more passive state to the cooler temperature or the effect of the machine’s vibrations on the window opening seal.

Now I’m wondering if it was simply related to the noise, as suggested by various studies, including the latest on mosquitoes’ reaction to electronic dance music.

Sound Disrupts Mosquito Behavior
It’s long been known that sound and its reception are crucial for reproduction, survival and population maintenance of many animals.


Mosquitoes mating in midair
(photo by C. Walcott, from
blogs.cornell.edu/harrington/aedes-mating/).
Over 150 years ago it was speculated that sound reception was involved with mosquito mating, which usually occurs in-flight. A 2006 study showed that interactive auditory behavior between the males and females--the tones produced by their wing-beat frequency--leads to sexual recognition. That and later studies established that mating success requires the male to harmonize its wing-beat tone with that of the female.

It was thought that the mosquitoes’ hearing mechanism--two feathery antennae--would limit sound reception to short distances; however, investigators from Cornell, Northwestern, Harvard and Binghamton universities recently determined that the sound of female wings buzzing sets males in motion up to 10 meters (about 33 feet) away.

Head of a male Anopheles mosquito; note antennae are inserted into doughnut shaped pedicel, the site of the Johnston’s hearing organ (from
www.nri.org/latest/news/2013/could-the-mosquito-s-buzz-be-its-downfall).
(Unrelated yet of interest, they also found that the frequency of human speech lies in the sweet spot of mosquito hearing sensitivity.) 

Mosquitos Don’t Like Dubstep
All this brings me to the study that found what is music to humans is noise to mosquitoes. A dubstep song by Skrillex had a major effect on mosquito behavior.

(Dubstep is a form of electronic dance music that originated in South London in the late 1990s. Sonny John Moore, known professionally as Skrillex, is an American record producer, DJ, singer, songwriter and musician. He has won eight Grammys, the most by an electronic dance music artist.)

Skrillex, the Grammy-winning electronic dance music artist (from www.magneticmag.com/2015/06/one-image-skrillex-will-change-your-perspective-on-life/).
The study was conducted by an international team of investigators led by researchers from the University of Malaysia, Sarawak. The goals were to provide insight into mosquitoes’ auditory sensitivity and examine the potential for music-based mosquito control measures.

In multiple 10-minute trials with different mosquitoes, the researchers subjected a cage of 10 hungry adult female mosquitoes to two conditions, music on or music off. In the cage with the females were a male mosquito for mating and a hamster as bait.

With the music off, the females visited the hamster much sooner and more often; attacked the hamster much sooner with much greater blood feeding; and copulated about five times more often. In other words, the dubstep music delayed the attack, reduced blood feeding and disrupted mating.

The mean (+/- standard error) time (seconds) before female mosquitoes first visited the hamster when dubstep music was off and on (from www.sciencedirect.com/science/article/abs/pii/S0001706X19301202).
Wrap Up
I should point out that the studies I’ve mentioned generally tested different mosquito species. The dubstep study, for example, used Aedes aegypti mosquitoes, a known vector of yellow and dengue fever viruses and other diseases.

The song used in the dubstep study (see P.S.) was chosen for its mix of very high and very low frequencies. Listening to it, I can understand why mosquitoes might be disrupted. I kind of liked it. See what you think. Anyway, at bedtime, I’d prefer to hear the air conditioner. Thanks for stopping by. 

P.S.
Example studies of mosquito communication:
1980: link.springer.com/article/10.1007/BF01953800
2006: www.cell.com/action/showPdf?pii=S0960-9822%2806%2901636-8
2009: www.nature.com/news/2009/091231/full/news.2009.1167.html
Dubstep mosquito study in Acta Tropica journal: www.sciencedirect.com/science/article/abs/pii/S0001706X19301202
Articles on dubstep study on BBC and LiveScience websites:
www.bbc.com/news/newsbeat-47770982
www.livescience.com/65125-mosquitoes-dont-care-for-skrillex.html
Mosquito hearing distance study in Current Biology journal: www.cell.com/current-biology/fulltext/S0960-9822(19)30028-4
Dubstep and Skrillex:
en.wikipedia.org/wiki/Dubstep
en.wikipedia.org/wiki/Skrillex
Dubstep mosquito study music, Scary Monsters and Nice Sprites: www.youtube.com/watch?v=WSeNSzJ2-Jw

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