Mosquito Magnetism

The science of selective biting

I love to hate mosquitoes,” says Ali Afify, an assistant professor of biology at Drexel University. “I think they are very interesting insects to study. They are unique in certain things, and they are the most dangerous animal because they kill more people than any other.”

Prof. Afify and I have something in common: we are both mosquito magnets. I mostly feel annoyance toward the tiny bloodsuckers. But after learning about Afify’s research on mosquitoes’ sense of smell, I can see where his fascination comes from.

Although it seems to me like mosquitoes’ sole purpose in life is to bestow itchy welts, they also have a critical role in the food chain. They drink nectar and therefore can pollinate flowers. And they are a food source for an incredible variety of wildlife: frogs, birds, fish, insects, and even carnivorous plants.

Not all mosquitoes are harmful: out of 3,500+ species, barely 6%  feed on humans. Some mosquitoes — in fact most — are vegans, feeding on plants rather than animals. Some actually eat other mosquitoes and their larvae. According to the CDC, out of two hundred types of mosquito that live in the U.S., only twelve can carry human diseases.

Many mosquito-born diseases don’t typically circulate in the U.S (except for Florida) — these include malaria, dengue, yellow fever, and Zika. Only West Nile seems to have a foothold in the US, with about 2,000 human cases annually in recent years. In our own neck of the woods, Philadelphia County had eleven human cases of West Nile in 2022. This year, Philly was named 7th in a list of top US cities where mosquitoes are a public health issue.

Female mosquitoes use a variety of senses to locate their blood meals and decide where to lay eggs. Body heat, body odor, the carbon dioxide we exhale—all of these attract mosquitoes to bite us. But why do some people get eaten alive, while others are rarely bitten? “Probably everyone has the same attractive chemicals on their skin, but the ratios change,” says Afify. “Some people have more of a specific chemical than others. And this is what makes them more attractive than other people.”

It’s not the most satisfying answer to a mosquito magnet like me. The exact compounds that cause this attraction are not well known. And even if they were, I doubt I could get my body to stop making so much of them. So I’ll have to use the old tried-and-true methods of keeping mosquitoes off my tasty skin. “One of the things that we always advise people is to wear long clothes to cover up the skin that can be bitten by mosquitoes,” says Afify. Their proboscises can’t poke through most fabrics, and you can also purchase treated clothing — a  quick search for “mosquito repellant clothing” will turn up pages of options.

“If you go outside and you see a container filled with water, I can guarantee you in no time in summer, it will collect many larvae—mosquito larvae—and those will become mosquito adults that come and bite you,” our mosquito researcher warns. The PA Department of Environmental Protection recommends regularly emptying any containers in your yard that collect standing water, even as small as a bottle cap.

I asked Prof. Afify about mosquito repellents. “I don’t use it on myself if I’m here in the U.S.,” he says. “But if I go to a place where there’s mosquito borne diseases like malaria, I would definitely use something that contains strong repellents like DEET.” The CDC recommends repellents that use DEET, picaridin, oil of lemon eucalyptus, or one of few other approved ingredients. Some of these work by masking attractive smells, making us “invisible” to the mosquitoes, and others have smells that the bugs actively avoid.

There are mosquito-trapping machines that use carbon dioxide — the gas we exhale when we’re breathing — to lure blood-sucking insects to their death. Other traps eradicate them at the egg or larval stage. None of these is a perfect solution, but unlike useless bug zappers, they’ve all been proven to make a considerable dent in an area’s mosquito population. Combatting these buggers is an on-going and multi-pronged strategy.

Since I live in a low-risk area for mosquito-borne diseases, my concern is mostly avoiding the discomfort of their bites, which I can acquire by the dozen if I go outside at dusk without any protection. Even though I would be glad to have fewer mosquitoes in the world, I can at least agree with Prof. Afify that they are interesting insects. “I don’t actually love them but I love studying them,” he says.

I guess you could say we both have a certain itch for these fascinating creatures. 😆

🦟Five Fun Facts About Mosquitoes🦟

  1. Worldwide, there are nearly 16,000 mosquitoes for every human
  2. Mosquitoes are attracted to people because they release carbon dioxide, lactic acid, and heat
  3. A female can feed five to six times in one day
  4. The lifespan of a male mosquito is 6 or 7 days; females can live up to five months
  5. Antarctica is the only place on earth with no mosquitoes

🙌🌎 WORLD MOSQUITO DAY (August 20) 🦟🦟🦟

World Mosquito Day marks the anniversary of Sir Ronald Ross’s discovery that mosquitoes transmit the parasite that causes malaria.

In 1897, Ross discovered the malaria parasite in the stomach tissue of an Anopheles mosquito. His work later confirmed that mosquitoes are the vector that carries this devastating parasite from human to human.

Today, more than 120 years later, mosquito-borne diseases cause hundreds of thousands of deaths each year. According to the World Health Organization, malaria alone leads to approximately 400,000 deaths annually.

To learn more, click the links in this post or reach out in the Comments field below with your questions. Please share your best mosquito tips and tricks: AntihistaminesWristbands? Ultrasonic waves?  “Skin So Soft“? Thank you for your thoughts and feedback.  🙏🙏🙏

About Anne Hylden 3 Articles
Anne Hylden holds an M.S. in Inorganic Chemistry and is pursuing an M.A. in Science Writing. She taught math and chemistry for twelve years before turning to freelance writing. When she's not thinking about science, she enjoys drinking tea, walking her dog around Northwest Philly, and laughing with her partner Bob.

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