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How to identify it
- Adults are small, dark flies, barely visible, with short, stocky bodies and a shiny thorax; up close they look like miniature mosquitoes.[1][2]
- They are small enough to pass through ordinary window screens.[1][2]
- Only females bite, because they need blood to develop eggs; both sexes feed on flower nectar.[1][2][3]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Mosquitoes | Much larger; a no-see-um looks like a smaller, more compact mosquito.[2][1] |
| Non-biting midges | Mosquito-like flies that swarm near ponds and lights but do not bite; they belong to a different family, the Chironomidae.[4] |
Where it lives
Culicoides biting midges occur worldwide. In the U.S. they are common near springs, ponds, lakes, rivers, beaches, swamps and marshes and are also reported from plains and mountains; Culicoides furens is a widespread coastal nuisance species. Most U.S. survey work has covered the West and Florida, and a 2022 to 2024 survey found 15 species in Arkansas.[8][1][3][9]
Biology and life cycle
Females feed mainly early and late in the day; Arizona sources say they are most active at dawn or dusk and in largest numbers in summer, and they can occur year-round where winters are warm.[3][1][2]
Eggs are laid in dark, damp places rich in organic matter: mud at the edges of ponds, streams and swamps, over-irrigated turf and mulch, tree holes, construction sites, splash pads, potted plants and even air-conditioner water.[1][2][3]
Larvae are semi-aquatic and feed on organic matter; they cannot survive drying out or more than about 2 inches of water. The life cycle takes about 2 to 6 weeks, depending on species and conditions.[1][2]
Females can disperse a little over a mile, but bites are usually heaviest close to where they emerge.[1]
Health risk
Arizona Extension describes the bites as small, intensely itchy red welts or water-filled blisters that can bleed when scratched. MedlinePlus says insect bites can cause pain, redness, swelling and itching and, in some people, severe allergic reactions that need emergency care. CDC says Oropouche virus is spread to people mainly by the biting midge Culicoides paraensis in South America, Central America and the Caribbean. In North America, Culicoides midges spread bluetongue and epizootic hemorrhagic disease viruses among cattle, sheep and deer.[1][5][6][7][8]
Control
Prevention
Find and dry out breeding sites: hold off irrigation near areas with many bites, let wet spots drain, and get rid of stagnant water rich in organic matter. Spraying larval sites isn't practical because they are hidden and scattered.[1][2]
Use a repellent registered for biting midges, such as DEET, and follow the label.[1][2]
Wear light-colored long sleeves, pants, socks and a hat with fine mesh netting where they're active; a head net helps where they are bad.[1][2]
Keep them out
Keep doors and windows shut and screened and repair rips. Standard 16 x 16 or 18 x 16 mesh screens don't stop them, so use finer mesh; Arizona Extension suggests 30 x 30 and Clemson 20 x 20 or smaller.[1][3]
Traps and physical control
A fan on a porch or patio helps keep them from flying in around you.[2]
Where sources disagree
Size: Arizona's IPM short gives adults as 1/8 to 1/4 inch long; Arizona's Backyard Gardener column says less than 1/16 inch, and Clemson says around 1/16 inch.[1][2][3]
Repellents: Arizona's IPM short says repellents that work on mosquitoes work on biting midges; the Backyard Gardener column says DEET seems only marginally effective against them.[1][2]
Screen mesh: Arizona suggests 30 x 30 mesh; Clemson says 20 x 20 or smaller can exclude them.[1][3]
Egg hatch: Arizona's IPM short says eggs hatch in 2 to 10 days; the Backyard Gardener column says in as little as 3 days.[1][2]
Common questions
- How do I treat no-see-um bites?
- MedlinePlus says to wash the bite with soap and water, apply ice wrapped in a cloth for 10 minutes on and 10 minutes off, and use an antihistamine or anti-itch cream if needed, then watch for signs of infection. Call 911 for trouble breathing or swelling of the face, mouth or throat.[5]
- Can no-see-ums get through my window screens?
- Yes. Standard 16 x 16 and 18 x 16 mesh lets them through; replace it with finer no-see-um mesh and keep doors closed.[1][2][3]
- Can I spray to get rid of no-see-ums?
- Area-wide control is nearly impossible, and their breeding sites are too scattered to treat; drying out wet spots, fine screens, clothing and repellents work better.[3][2][1]
Sources
- University of Arizona Cooperative Extension, “Something's biting me, but I can't see it! (No-See-Ums IPM Short, June 2018).” cales.arizona.edu/apmc/docs/No-See-Ums-IPMShort.pdf (accessed 2026-11-11)
- University of Arizona Cooperative Extension, ““No-See-Um” Biting Flies (Backyard Gardener #59, January 15, 2023).” extension.arizona.edu/sites/extension.arizona.edu/files/barnesm/No-See-Um.pdf (accessed 2026-11-11)
- Clemson Cooperative Extension, Home & Garden Information Center, “Gnats (HGIC).” hgic.clemson.edu/factsheet/gnats/ (accessed 2026-11-11)
- Clemson Cooperative Extension, Home & Garden Information Center, “Midges (HGIC).” hgic.clemson.edu/factsheet/midges/ (accessed 2026-11-11)
- MedlinePlus, U.S. National Library of Medicine, “Insect bites and stings (Medical Encyclopedia).” medlineplus.gov/ency/article/000033.htm (accessed 2026-11-11)
- Centers for Disease Control and Prevention, “About Oropouche.” www.cdc.gov/oropouche/about/index.html (accessed 2026-11-11)
- Current Tropical Medicine Reports, via PubMed, “McGregor, Shults and McDermott (2022), A review of the vector status of North American Culicoides for bluetongue virus, epizootic hemorrhagic disease virus, and other arboviruses of concern.” pubmed.ncbi.nlm.nih.gov/36105115/ (accessed 2026-11-11)
- Journal of Medical Entomology, via PubMed, “Steele and McDermott (2026), The Culicoides of Arkansas: a species checklist and comparison of diversity across ecoregions and habitats.” pubmed.ncbi.nlm.nih.gov/41804047/ (accessed 2026-11-11)
- Scientific Reports, via PubMed, “Montenegro et al. (2025), Laboratory and field assays indicate that a widespread no-see-um, Culicoides furens, is susceptible to permethrin.” pubmed.ncbi.nlm.nih.gov/39922977/ (accessed 2026-11-11)
- iNaturalist, “Culicoides taxon page (order and family).” www.inaturalist.org/taxa/122218 (accessed 2026-11-11)