In Defense of Mosquitoes

Photo by Alexandra Westrich, The Field Museum

August 20 is World Mosquito Day, but it’s not exactly a holiday celebrating them. It commemorates the day of the 1897 discovery that female mosquitoes transmit malaria, and it doesn’t paint them in a very positive light.

“It’s funny—World Mosquito Day is mostly about getting rid of mosquitoes,” says The Field Museum’s resident mosquito expert, Alexandra Westrich, a research associate here and the contract supervisor at the Chicago Department of Public Health, where she oversees lab and field work surrounding West Nile virus.

Getting rid of mosquitoes has been a topic of debate for years—some groups advocate for the eradication of the species of mosquitoes that carry human diseases. They’ve got a point—mosquitoes can carry deadly diseases malaria, dengue fever, yellow fever, West Nile virus, and Zika. According to the Bill Gates Foundation, mosquitoes cause more human deaths than any other animal, including other humans.

“Even among entomologists, mosquitoes are pretty unpopular. I hate them and I love them,” admits Westrich. But, she notes, they’re not all bad.

Mosquitoes are known for being blood-suckers, but they eat mostly nectar. The only mosquitoes that bite you are females that are getting ready to produce eggs—they need the extra nutrients they get from blood meals. So, they’re not bloodthirsty—they’re just being good moms. Male mosquitoes and non-fertilized females only eat nectar, helping pollinate plants in the process.

When a mosquito mom is out for blood, she uses the fine hairs on her antennae to scent prey. “Mosquitoes find their prey by seeking out carbon dioxide—when you exhale a lot, like when you’re exercising, you put out more CO2, which attracts mosquitoes,” explains Westrich. So, you heard it from The Field Museum first—don’t exercise, and don’t go outside. But if a 100% indoor lifestyle isn’t feasible for you, Westrich notes that you can avoid mosquito bites by wearing bug spray, long sleeves, and pants. Meanwhile, you can get rid of mosquito breeding grounds by dumping out any containers of standing water on your property.

And, while most of the mosquitoes in Chicago are pretty non-descript, some of their relatives are real lookers. “There are lots of beautiful mosquito species,” says Westrich. “Elephant mosquitoes have red and pink scales, and Uranotaenia sapphirina have iridescent blue scales—they don’t bite humans, they have a preference for frogs.”

 Beyond their roles as pollinators and borderline-pretty insects, Westrich notes that eradicating them could have unforetold effects upon the ecosystem at large. “As a scientist, I’m uncomfortable with the notion of wiping out a species, even one that harms as many humans as some mosquitoes. You never know what other organisms their extinction would impact.”

When asked if mosquitoes’ good qualities outweigh the bad, Westrich laughed. “No, they’re the bane of humanity. But I can admire the way they’ve evolved with humans. And mosquito-borne diseases make them a good check on human population growth. It sounds terrible, and it’s not good for us, but it’s good for the planet and the other species we live with.”