A new study by mechanical engineering researchers at the University of Central Florida explored how yellow fever mosquitoes (Aedes aegypti) look for mesh holes. (Image originally published in Dickerson et al. 2018, Insect Science Journal)

Author: Leslie Mertz, PhD

It was a hot and humid summer night. The windows were open and the breeze came in. When you heard the maddening buzzing of mosquitoes in your ears, you started to fall asleep. After a few unsuccessful slaps on the side of your head, you turn on the light and see a small hole in the window screen. While chasing the tormentor in the next 15 minutes, you will ask yourself how the mosquito found such a tiny gap and sneaked into your house.

For Dr. Andrew Dickerson, assistant professor of mechanical engineering at the University of Central Florida, this question has become a research project: How do mosquitoes identify tiny gaps, especially holes in mosquito nets used in tropical areas, to exclude dangerous pathogenic species? "We know that mosquito nets will be torn, but we don't know to what extent they become ineffective," he said. "Although we are not the first to study this issue, we are the first to look at it the way we currently do."

The surprising results were published in the "Insect Science Journal" last week.

Dickerson and his students applied their expertise to the gap detection ability of yellow fever mosquitoes (Aedes aegypti). "Engineers can bring a physical understanding of what is happening to this type of problem. This includes the use of physical and engineering tools to describe the behavior of insects, because after all they are like small robots or small airplanes, if you want," Dixon Say.

Their experimental device consists of a 2-foot-long acrylic tube with a diameter of 6.5 inches in which mosquitoes can fly. Before adding the mosquitoes, they installed a mosquito net on the last third of the pipe and placed an attractant behind it.

The attractant is a bit of a dilemma. "If you look at the literature on mosquitoes, you will find that people attract mosquitoes in different ways, partly because different species respond to different attractants," Dixon said. He chose the method outlined in a scientific paper he discovered in his research: a dirty sock. (For consistency of experiment, the same undergraduate wears socks for at least 12 hours before each experiment.) He also consulted with UCF mosquito experts. He pointed out that heat and humidity are strong attractants for yellow fever mosquitoes, so they Added a beaker of hot water next to the sock. Dixon said: "Because of the smell of human socks plus heat and humidity, we think mosquitoes are irresistible."

Dixon said the researchers experimented with carefully cut holes — ranging from 8 millimeters (mm) to 20 millimeters — and found some surprising things about mosquito strategies. First, the mosquito will fly to the attractant quickly, but it cannot find the hole through the line of sight. On the contrary, it is entirely accidental. It flies to the Internet, bounces off, and then redirects to fly to the Internet again, or take a break, most of the time just standing there. In fact, Dixon pointed out that mosquitoes seem to like to fly by flying very much, and the crawling distance is very small, so they are more likely to fly through holes instead of crawling through them. For gaps smaller than the width of the mosquito's flight, occasionally you will see landing and crawling over the gap.

Second, the mosquitoes will stick to the same area of ​​the mosquito net. "Each time they approach the net, the approach position will be affected by where they were in the previous approach," he explained. In other words, if the mosquito does not approach the hole on the first attempt, it may never find the hole. Third, the size of the hole is very important. Mosquitoes do not sneak into the 8mm gap even if they can on the body, and they prefer 10mm gaps to larger holes.

A new study by mechanical engineering researchers at the University of Central Florida explored how yellow fever mosquitoes (Aedes aegypti) look for mesh holes. Studies have shown that mosquitoes prefer to travel by air and crawl for a short distance; in this study, they are more likely to fly through holes rather than crawl through them. The video shown here slows down to 1/17th of actual speed. (The video was originally published in the 2018 supplement of Dickerson et al., Insect Science Journal)

There is still a lot to know about how mosquitoes pass through mosquito nets. Dickerson said he hopes to study some related topics one day, including why 10 mm is the best point for hole size and how insecticide-treated mosquito nets affect the passage. "I do think this is an important job, but I just need to find someone to fund it," he said.

On a personal level, Dickerson admitted that the results of the research, especially seeing the important role of opportunity in allowing mosquitoes to find emptiness, made him more calm when relaxing on a screened porch (or veranda) in hot weather. And humid Florida: "This study really made me feel more at ease. Now, if there is a hole in my balcony, I won't worry about it as much as in other situations."

"Aedes aegypti (Diptera: Culicidae) mosquitoes enter the space lower than expected by random search"

Dr. Leslie Mertz teaches summer field biology courses, writes articles about science, and runs an educational insect recognition website www.knowyourinsects.org. She lives in northern Michigan.

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The number of mosquitoes in many parts of the world is surprisingly high. Therefore, even if they are not good at deductive reasoning when looking for holes, the sheer number of mosquitoes makes one or more people sure to accidentally find and infect people with any potential number of viruses. Types of microorganisms can infect chikungunya, dengue fever, elephantiasis, malaria, West Nile virus, yellow fever, Zika virus, etc.

This is why effective and inexpensive pesticides that everyone can use are absolutely necessary.

It's all about numbers, not holes!

For biological insecticides, mosquito repellent plants should be used.

Unfortunately, they don't work very well :(

I just woke up and found a big mosquito in the net. I will never see the hole in my life! This is too mysterious for me, I am fascinated by it now!

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