No-see-ums are tiny biting midges (family Ceratopogonidae), so small most people never see one bite. Only females bite, mostly around dawn and dusk near water, marshes and soggy ground. To get rid of them around your home, let wet spots dry out, use fine-mesh screens, run a fan, and wear repellent at golden hour.
Once you know where they come from and when they fly, you can take back the best part of the day: that slow, warm stretch on the porch or the beach as the sun goes down. Here is what university entomologists say, and a Saturday checklist to keep you outside.
What are no-see-ums?
No-see-ums are small biting midges in the genus Culicoides, family Ceratopogonidae, order Diptera, the same order that includes mosquitoes and other biting and non-biting flies (University of Arizona Extension). You will also hear them called punkies, sand gnats or sand flies. Many people only ever meet them through the bites and wonder what bit them.
About that "sand fly" name: UF/IFAS Extension says biting midges "are sometimes incorrectly referred to as sand flies," because true sand flies are a different group of insects. In Australia, though, "sandflies" is the everyday word for biting midges, which is why we cover them separately in our guide to sandflies in Australia.
University of Florida entomologists count over 4,000 species of biting midges, over 1,000 in Culicoides, and 47 in Florida.
How small are no-see-ums, really?
This is where the experts politely disagree:
- University of Arizona Extension: small, dark flies 1/8 to 1/4 inch long, barely visible to the naked eye. Up close they look like miniature mosquitoes.
- UF/IFAS Extension: gray, and less than 1/8 inch long.
- Clemson Extension: around 1/16 inch, so most people never see one feed. Hence the nickname.
Whichever number you go with, the takeaway is the same: they are small enough to slip past you, and past an ordinary window screen.
The no-see-um life cycle
According to UF/IFAS Extension and University of Arizona Extension:
- Eggs are laid in dark, damp spots rich in organic matter, inside or outside buildings. They cannot withstand drying out, and hatch in 2 to 10 days.
- Larvae are semi-aquatic and cannot survive a total lack of moisture or more than 2 inches of water (Arizona). UF says this stage lasts from two weeks to a year.
- Pupae last about 2 to 3 days.
- Adults live only a few weeks in nature.
Egg to adult takes roughly 2 to 6 weeks, depending on species and conditions. That moisture dependence is the key to everything below.
Where no-see-ums live and breed
University of Arizona Extension says no-see-ums turn up in almost any habitat near water: springs, ponds, lakes, river banks, beaches and swamps. UF/IFAS Extension adds that "coastal areas provide primary habitat for biting midges," with larvae in and around salt marshes, mangrove swamps, stream and pond shores, and muddy ground.
Closer to home, Arizona lists over-irrigated mulch and turf, tree holes, new construction sites, splash pads and poorly drained areas, indoor potted plants, and even water from air conditioners.
Females may disperse a little over 1 mile, but high numbers of bites are likely very close to where they emerge (University of Arizona Extension). So a lot of bites on your porch usually means a soggy spot nearby.
When no-see-ums bite
Only adult females bite, since they need blood to produce eggs (University of Arizona Extension). They are most active:
- Dawn and dusk. All three extension services point to early morning and evening.
- Cloudy, calm days. UF/IFAS Extension notes they can bite in daytime when it is overcast and still.
- Summer, and sometimes all year. Numbers peak in summer, but where winters are warm they can occur year-round (Arizona). Worth knowing before a winter trip to Florida.
- Until the first frost. In South Carolina, the first killing frost of fall brings welcome relief (Clemson Extension).
Clemson describes the bite as an itchy raised spot similar to a mosquito bite, and UF/IFAS Extension notes that in the US no-see-ums are primarily a nuisance. If you want to know what the bites look like, see our guide to no-see-um bites.
How to get rid of no-see-ums around your home
You cannot clear a whole marsh, but you can make your own yard and porch a much calmer place.
1. Let the wet spots dry out
This works at the source. University of Arizona Extension advises that if you are getting a lot of bites, hold off on irrigation nearby and let moist spots drain and dry. In their words, "This will kill eggs and larvae."
2. Upgrade your screens
Ordinary 16 x 16 or 18 x 16 mesh lets no-see-ums through (Arizona). Arizona suggests 30 x 30 mesh where possible, and Clemson recommends very fine mesh, 20 x 20 or smaller, for porches. UF notes the tradeoff: smaller mesh limits airflow. Keep doors shut, do not prop them open, and repair rips or gaps.
3. Turn on a fan
Because no-see-ums are so small and are weak fliers, UF/IFAS Extension says ceiling and window fans on high can keep them out of small areas. Clemson suggests a ceiling fan under a covered porch, or a box fan, since they are small enough to be blown off course.
4. Know why spraying the yard does not last
People often ask what gets rid of no-see-ums instantly. UF/IFAS Extension says insecticide sprays for adults "are not efficient": they may knock down the midges active that night, but more keep arriving from breeding areas, so some places would need daily applications. Clemson says area-wide control is nearly impossible for the same reason. Drying, screening and fans do the steady work instead.
What three university extension services say
None of the top guides we read put these side by side, so we did. Where they disagree, the table shows each answer.
| Topic | University of Florida (UF/IFAS) | University of Arizona | Clemson (South Carolina) |
|---|---|---|---|
| Adult size | Less than 1/8 inch, gray | 1/8 to 1/4 inch, dark | Around 1/16 inch |
| When they bite | Early morning and evening; daytime on cloudy, calm days | Dawn or dusk; peak in summer, year-round where winters are warm | Early and late in the day; relief after the first killing frost |
| Where they breed | Salt marsh, mangroves, stream and pond shores, muddy ground; coasts are primary habitat | Any muddy or moist spot: over-irrigated turf and mulch, splash pads, tree holes, indoor pots, AC water | Swamps, marshes, ponds and stream edges; eggs laid in mud |
| Screen mesh | Smaller than 16-mesh (smaller mesh limits airflow) | Replace 16 x 16 or 18 x 16 with 30 x 30 | 20 x 20 or smaller for porches |
| Fans | Ceiling and window fans on high | Not covered in the guidance we used | Ceiling fan on a covered porch, or a box fan |
| Spraying for adults | "Not efficient"; more keep arriving | Focus is on drying breeding spots | Works briefly, but would likely be needed daily |
The pattern is clear: moisture is the source, fine mesh and moving air are the defense.
Can no-see-ums get in your house?
Yes. University of Arizona Extension says they pass through ordinary screens, occasionally bite indoors, and can breed in wet indoor potted plants.
The good news: UF/IFAS Extension says they "do not establish inside homes, apartments." If you notice bites indoors, let potted plants dry between waterings, check your screen mesh, keep doors closed at dusk, and run a fan. For more, see our indoor repellent guide.
No-see-ums vs gnats
Clemson Extension explains that two different small flies both get called gnats:
- Biting gnats (sand gnats or no-see-ums) are biting midges. Females bite, mainly early and late in the day.
- Eye gnats (family Chloropidae) do not bite. They are around 1/8 inch, swarm around faces, and are common in loose sandy soil. For them, 18 x 16 mesh is usually enough.
So little flies hovering around your face without biting are probably eye gnats. Bites from something you cannot see are probably no-see-ums.
Keep them off your skin
For sunset itself, repellent and clothing fill the gap. University of Arizona Extension puts it simply: "Repellents effective against mosquitos are effective against biting midges." Choose a suitable repellent and always follow the label.
For reference, the CDC lists these active ingredients for EPA-registered insect repellents, framed for mosquito bite prevention: DEET; picaridin (icaridin outside the US); IR3535; oil of lemon eucalyptus (OLE), plant-derived; para-menthane-diol (PMD); and 2-undecanone, plant-derived.
Arizona also suggests light colored long sleeves, pants, shoes and socks, and a hat with fine mesh netting. For a side-by-side look at sprays, read our best bug spray for no-see-ums guide.
Your Saturday no-see-um checklist
Here is the table turned into one easy morning, coffee in hand.
- Walk the yard for wet spots. Overwatered beds, soggy mulch, low spots in the lawn, the drip under the AC unit. Ease off the sprinklers and let them dry.
- Check the potted plants, indoors and out. Let the soil dry between waterings.
- Look at your screen mesh. If it is standard 16 x 16 or 18 x 16, plan finer mesh for the porch. Patch any rips today.
- Set up a fan on the porch, ceiling fan on high or a box fan across where you sit.
- Stage your repellent by the door for golden hour, plus long sleeves for evenings you plan to linger.
- Planning a coastal trip? UF/IFAS Extension notes visitors can check how close a spot is to midge-producing areas such as salt marsh.
Then do the best part: be back on the porch for sunset.
Our pick for porch and beach evenings
We made Bloc Off Mosquito Repellent Spray for exactly these golden-hour moments. It uses 8% plant-based PMD (para-menthane-3,8-diol) derived from lemon eucalyptus, with 6+ hours of lab-tested protection against mosquitoes, ticks and other biting insects, per our product page. It is DEET-free and alcohol-free, with aloe vera and chamomile, in a 4 oz (118 ml) bottle for $15.00.
My co-founder and formulator Cassidy Huang and I spent two years with a Taiwan-based chemist developing it. Shiso (perilla) adds a gentle feel and clean herbal scent; the protection comes from the PMD.
For beach bags and travel, Bloc Off Mosquito Repellent Wipes come as 10 individually wrapped wipes for $13.00.
FAQ
Do no-see-ums bite?
Yes, but only the females, which need blood to produce eggs. Both sexes feed on pollen and nectar, and males are not a biting concern (University of Arizona Extension).
What gets rid of no-see-ums instantly?
Nothing lasts instantly. UF/IFAS Extension and Clemson Extension both say sprays for adults are quickly undone by new midges arriving from breeding areas. Letting moist spots drain and dry works at the source, since University of Arizona Extension says it kills eggs and larvae.
Does vinegar or a certain smell get rid of no-see-ums?
None of the university extension sources we used recommend vinegar or any scent. What they do recommend is drying out breeding spots, fine-mesh screens, fans, and a repellent used according to its label.
Can no-see-ums live in your house?
They can get in and breed in wet indoor potted plants (University of Arizona Extension), but UF/IFAS Extension says they do not establish inside homes or apartments.
Are no-see-ums the same as sand flies?
Not technically. UF/IFAS Extension says biting midges are sometimes incorrectly called sand flies, since true sand flies are a different group. In Australia, "sandflies" is the common name for biting midges, which we cover in our sandflies in Australia guide.
Written by Tanya Lee, Co-Founder of The Superbloc. Sources: University of Arizona Cooperative Extension, "Something's biting me, but I can't see it!" (Nair, Gouge, Li, 2018); UF/IFAS Extension EENY 349, "Biting midges, no-see-ums Culicoides spp." (Connelly, revised 2013); Clemson Cooperative Extension HGIC 2489, "Gnats" (Ballew, 2018); CDC, "Preventing Mosquito Bites."