You’re enjoying a relaxing walk or outdoor meal when suddenly, tiny bugs start swarming around you, ruining the summer moment as you frantically swat them away—sound familiar?
Summer is prime mosquito season, but the warm weather also brings its fair share of gnats and other small flies. These bugs often swarm, especially around our faces, and can occasionally even bite.
So what exactly are these tiny insects, and why are they so attracted to us? And, most importantly, what can you do to keep them away? Here’s what experts had to say.
The term “gnat” is most commonly used to describe the little flying insects that bother us, but people often use the word too broadly, Sarah Hughson, PhD, an insect and arthropod diagnostician with Michigan State University Plant and Pest Diagnostics, told Health.
“The colloquial usage of the word gnat is very different from the way entomologists [insect experts] use this word,” said Hughson. “Many people use the word ‘gnat’ to describe any small fly.”
Flies typically have six legs, two wings, and don’t sting, she said, and there are thousands of species. But only two groups of these flies are actually considered “gnats” by entomologists, she said.
These two insect groups—fungus gnats and black gnats—are particularly bothersome in the summer, along with flies known as “midges,” Hughson explained.
Here’s a bit about each.
Fungus Gnats
There are many varieties of fungus gnats, but two common ones are Mycetophilidae and Sciaridae. Per the name, these little flies are attracted to fungus-like mushrooms that grow in organic matter, Changlu Wang, PhD, an extension specialist in entomology at Rutgers University, told Health.
Fungal gnats are found throughout the U.S., particularly in gardens, woodland areas, or other places with soil and decaying organic matter, added Hughson.
They’re not known to bite people, and are largely considered nuisance pests.
Black Gnats
Also known as “black flies” or “buffalo gnats,” these insects belong to the Simuliidae family. There are dozens of species.
Some species bite, while others swarm without biting. Among those that do feed on humans, only the adult female black gnats bite. They usually go after exposed skin along the hairline, feet, ankles, and arms.
Black gnats are most commonly found around areas with water, said Hughson.
Midges
These tiny flies belong to the order Diptera—and they’re not gnats. Though midges look like mosquitoes, most species don’t bite or carry disease. These harmless midges, called Chironomidae, tend to swarm around streams, ponds, and lakes, especially in the late afternoon or evening.
But another family of midges, termed Ceratopogonidae, can cause more issues. These biting midges, also in the order Diptera, are much smaller and don’t resemble mosquitoes as closely.
Again, it’s the adult females that feed on humans. These bugs can also transmit a certain type of parasite that can infect humans. However, these cases have only been reported in Central America, South America, and the Caribbean.
In general, biting midges can be found across the U.S., but they’re concentrated primarily in coastal areas, farming sites, mangrove swamps, and salt marshes.
For most of these tiny flies, swarming is actually a mating behavior, Hughson explained.
“Emerging around the same time allows them to fly together in groups and mate,” she said. “The adults are usually only active for a short time, a few days or weeks, so it is important for them to find mates quickly and lay eggs before they die.”
Like mosquitoes, gnats and small flies are attracted to our body temperature, smell, and breath, which is why they tend to swarm around humans and other animals, explained Wang. They’re also very attracted to moisture, making our eyes, noses, and mouths especially tempting targets, he added.
As for why this only seems to be an issue in the summer? The high temperatures make it easier for gnats and other small flies to develop faster and find food, said Wang.
These swarming bugs can be really bothersome, but they aren’t particularly dangerous. “They’re mostly a nuisance,” Wang explained.
That even goes for the biting midges and black gnats that try to feed on humans—the bites aren’t usually threatening to your health in any way, Hughson added.
“Certain species can carry disease to livestock like sheep and cattle, but they don’t cause disease in humans in the U.S.,” although they can in certain other areas of the world, said Wang.
If you do get bitten by a small fly, sensitivity may vary—some people feel next to nothing, while others might experience:
- Itchiness
- Redness
- Irritation
- Swelling
Gnats and other tiny flies may not be dangerous, but they are often hard to avoid.
Unlike many types of insects, gnats and midges aren’t attracted to food, drinks, or scents from personal care products, Wang explained, so making changes there won’t have any effect.
Plus, even bug sprays aren’t guaranteed to work.
Insect repellents are designed to keep blood-sucking bugs away by impeding their ability to find humans to bite. “But for flies and gnats, because they’re not biting, repellent has very little effect,” said Wang.
That being said, though, DEET, picaridin, oil of lemon eucalyptus, and other repellents can all be effective against those flies and gnats that do bite, Hughson explained.
“Keep in mind that the animals must come in contact with these materials to be repelled, so they will touch your skin to make contact, then leave without biting,” she added.
Overall, there’s not a lot you can do to completely avoid gnats and tiny flies, other than staying away from areas where they congregate.
But there are some strategies to lower your risk of being bitten:
- Cover up. Wearing loose long-sleeved shirts and long pants makes it more difficult for insects to bite you, advised Hughson.
- Wear light colors. White or brightly colored clothing is less attractive to some flies than darker clothing.
- Maintain areas around plants. Any accumulation of decaying, organic material raises your risk of attracting fungal gnats, said Wang.
- Avoid going out when they’re swarming. Flies tend to be most active at dawn and dusk, and on calm, non-windy days.
Though bites and swarming from tiny flies are annoying, Hughson said it’s important to remember that bugs are part of nature.
“Insect populations throughout the world are declining because of pesticide use, habitat loss, climate change, and other complex factors,” Hughson said. “If they are not harming your plants, home, or biting you, it would be beneficial and kind to take a live-and-let-live approach.”
