Midges and gnats are both tiny flies in the order Diptera, and the terms overlap so much that even entomologists use them loosely. The core distinction: “midge” usually refers to small flies with aquatic larvae (families Chironomidae and Ceratopogonidae), while “gnat” is a casual catchall for any small swarming fly, including fungus gnats (family Sciaridae), eye gnats, and buffalo gnats. Some biting midges are even called “gnats” regionally. Understanding which one you’re actually dealing with matters because it changes where they breed, whether they bite, and how you get rid of them.
Why the Names Are So Confusing
Neither “midge” nor “gnat” is a precise scientific term. They’re common names applied to dozens of fly families. In the American Southwest, biting midges go by “pinyon gnats.” In the Southeast, they’re called “five-O’s” because they tend to bite around 5 PM. Across much of North America, the same insects are known as “no-see-ums” or “punkies.” In Canada, some species are called “moose flies.” The overlap means you can’t reliably tell what someone is talking about from the name alone.
What actually separates these insects is their biology: where they breed, what they eat, and whether they can bite you.
The Main Types You’ll Encounter
Non-Biting Midges (Chironomidae)
These are the midges that swarm in clouds near lakes, rivers, and ponds at dusk. They look strikingly like mosquitoes, with long legs and feathery antennae, but they don’t bite. Their larvae develop in aquatic sediment, thriving in conditions ranging from clean streams to polluted, stagnant water. Urban areas with poor drainage, fertilizer runoff, or septic system overflow create ideal breeding sites. Under hot summer conditions, eggs hatch in as little as 72 hours. These midges are pure nuisance insects: they don’t feed on blood, don’t transmit disease, and die within days of emerging as adults.
Biting Midges (Ceratopogonidae)
This is the family that earns the “no-see-um” nickname. Over 4,000 species exist worldwide, though only four genera feed on mammal blood. Females have four tiny cutting blades inside a fleshy sheath that lacerate skin, producing a sharp, burning pain disproportionate to the insect’s size. Males lack functional biting mouthparts entirely. Both sexes feed on plant nectar for energy, but females need a protein-rich blood meal to produce eggs. Some females skip vertebrates altogether, instead capturing small insects and feeding on their body fluids.
Biting midge larvae develop in moist environments: mosses, algae, rotting logs, soil beneath cattle dung, and muddy shorelines. Some larvae are predators themselves, feeding on tiny worms, protozoa, and insect larvae.
Fungus Gnats (Sciaridae)
If you’ve seen tiny black flies hovering around your houseplants, these are almost certainly fungus gnats. They’re the most common “gnat” found inside homes and buildings. Adults are delicate, about 3 mm (roughly 1/10 inch) long, with a distinctive Y-shaped vein pattern on their wings. Their translucent larvae have a visible black head capsule and grow up to 5.5 mm long.
Fungus gnats don’t bite. They breed in moist, decaying organic matter, and indoor infestations are almost always tied to overwatered potted plants. Females lay eggs in damp soil, and larvae emerge 4 to 6 days later. The larvae spend 12 to 14 days feeding on fungi, organic debris, and plant roots before pupating. Outdoors, autumn provides optimal conditions for egg laying, but indoor plants and greenhouses support them year-round.
Quick Comparison
- Breeding habitat: Midges breed in aquatic or semi-aquatic environments (lakes, ponds, muddy soil). Fungus gnats breed in moist soil rich in organic matter, especially potted plants.
- Biting: Biting midges (no-see-ums) bite and draw blood. Non-biting midges and fungus gnats do not bite.
- Size: Both groups are small, generally 1 to 6 mm. Biting midges tend to be on the smaller end, sometimes nearly invisible.
- Where you find them: Midges swarm outdoors near water. Fungus gnats hover near plants, drains, and windows indoors.
- Attraction to light: Both midges and gnats are drawn to artificial light, which is why they cluster around porch lights and windows.
Bites: What They Look and Feel Like
Only biting midges leave marks on skin. The bite itself feels like a sharp, burning pinprick, surprisingly painful for an insect you may not even see. The resulting welts are small and raised, often appearing in groups because the insects tend to feed in clusters. The itch can persist for several days and, in sensitive individuals, can trigger swelling that looks more severe than a typical mosquito bite.
Fungus gnats and non-biting midges cause zero skin reactions because they physically cannot break skin. If you’re getting bitten indoors, you’re dealing with something other than fungus gnats, possibly biting midges that found their way inside, or another pest like fleas or bed bugs.
Disease Risk
Fungus gnats and non-biting midges carry no known human diseases. Biting midges are a different story. The family Ceratopogonidae can transmit Oropouche virus, which causes fever, headache, and joint pain. Outbreaks are typically small and non-lethal, but a 2024 strain in South America was linked to miscarriage, fetal deaths, and microcephaly. Biting midges also transmit bluetongue virus to livestock, a serious concern for sheep and cattle farmers. In North America, the disease risk from biting midges is low for most people but worth knowing about if you live in tropical or subtropical regions.
How to Keep Them Out
Standard window screens won’t stop biting midges. They’re small enough to pass through regular mesh. Specialty “no-see-um” screens use a tighter 20×20 mesh weave designed to block these insects along with sand flies and small gnats. If you live in a marshy or coastal area where biting midges are common, upgrading your screens is one of the most effective long-term fixes.
For outdoor protection, DEET-based repellents work well against biting midges, black flies, and mosquitoes. Picaridin is equally effective against biting midges and also repels chiggers. Oil of lemon eucalyptus (the active ingredient is PMD) is a plant-derived option registered for use against gnats, no-see-ums, black flies, and mosquitoes. Products containing IR3535 cover a broad range including biting midges, gnats, sand flies, and deer ticks.
For fungus gnats indoors, the fix is almost always about moisture. Let the top inch or two of potting soil dry out between waterings. Fungus gnat larvae need consistently damp, organic-rich soil to survive. Removing that condition breaks the breeding cycle within a couple of weeks. Yellow sticky traps near affected plants catch adults and help you monitor whether the population is declining.
Midges Near Water vs. Gnats Near Plants
The simplest way to figure out what you’re dealing with is location. Clouds of tiny flies near a pond, lake, or river at dusk are almost certainly midges, either the non-biting kind or, if you’re getting bitten, Ceratopogonidae. Tiny flies circling your houseplants, hovering near kitchen drains, or landing on windows inside your home are most likely fungus gnats.
If you’re outdoors in a wooded or marshy area and something bites hard but you can barely see it, that’s the classic no-see-um experience. These insects are most active at dawn and dusk, and wind is your best natural defense since they’re weak fliers. Even a light breeze or a fan on a porch can keep them away more effectively than most chemical approaches.