Gnats

What Does a Gnat Look Like Up Close?

Up close, a gnat looks like a tiny, thin mosquito. Most are 1/16 to 1/8 inch long, about the size of a grain of rice or smaller. The body is dark and slim, the legs are long, and there is one pair of clear or smoky wings.

“Gnat” is not one species. It is the everyday name for a dozen or so kinds of small flies. The common house gnat is the fungus gnat, so I’ll use it as the model. Under a hand lens or a zoomed-in phone photo, here is what you see:

• Two big compound eyes. They take up most of the head. On a fungus gnat the eyes meet in a narrow bridge above the antennae.
• Long, beaded antennae. The University of California notes that fungus gnat antennae are longer than the head. Fruit flies and drain flies have short, stubby ones.
• One pair of wings. All true flies have two wings, not four. Fungus gnat wings are light gray to clear, and the common kinds have a Y-shaped vein near the tip.
• Six long, thin legs. The legs look too long for the body, which is why people mix gnats up with mosquitoes.
• No biting beak on house gnats. A mosquito has a long needle out front. A fungus gnat doesn’t.

How big can gnats get? A few fungus gnat species reach 1/2 inch, but the same University of California guide says adults are commonly 1/16 to 1/8 inch. A “giant gnat” with a one-inch body and legs that snap off is a crane fly, and it doesn’t bite.

Types of Gnats: Identification Chart

Where you see the gnat tells you more than its color does. Start with the third column.

Type of gnat	What it looks like up close	Where you find it	Bites people?
Fungus gnats	Dark, thin, mosquito-like, long legs and antennae, about 1/8 inch	Houseplants, windows, lamps	No
Fruit flies	Tan to brown, rounder body, red eyes, about 1/8 inch	Ripe fruit, trash, recycling, sink drains	No
Drain flies	Gray and fuzzy like a tiny moth, 1/16 to 3/16 inch	Bathroom walls, sinks, floor drains	No
Phorid flies	Tan to brown with a humped back, about 1/8 inch, runs before it flies	Drains, trash, broken sewer lines	No
Eye gnats	Shiny black or gray, yellow-orange legs, 1/16 to 1/8 inch	Around your face outdoors, near sandy soil	No, but they feed at eyes and cuts
No-see-ums (biting midges)	Gray speck, about 1/16 inch	Near marsh, mud, and shorelines at dawn and dusk	Yes
Buffalo gnats (black flies)	Dark, stout, arched back	Near streams and rivers in the daytime	Yes
Non-biting midges	Mosquito look-alike with no beak; males have feathery antennae	Ponds and lakes, porch lights at night	No

Common Types of Gnats, by Where You Find Them

Types of Gnats in the House

Four small flies cause nearly all indoor “gnat” calls. The University of Kentucky lists the same four as the most common small flies in homes: fungus gnats, fruit flies, drain flies, and phorid flies.

• Fungus gnats are the true house gnat. They are dark with long legs and they hang around houseplants and wet potting soil. Larvae are clear to white with a shiny black head. A female can lay up to 200 eggs in the cracks of potting mix, according to Colorado State University Extension.
• Fruit flies are the tan ones with red eyes that hover over the fruit bowl. Entomologists don’t call them gnats, but most people do. One female can lay over 500 eggs, and the Kentucky fact sheet says the whole cycle takes 8 to 10 days at 77°F. That is why they seem to show up overnight.
• Drain flies, also called moth flies, look like tiny gray moths. They hold their wings like a roof over the body and sit on the wall near a sink or shower. They move in short hops.
• Phorid flies have a humped back. NC State Extension says they “run erratically across surfaces rather than flying.” They breed in rotting, wet material, and a lot of phorid flies in one room can point to a broken drain line.

Not sure which one you have? Our comparison guides walk through the look-alikes: gnats vs fruit flies, drain flies vs gnats, and fungus gnats vs drain flies.

Gnats That Bite

Only a few gnats bite, and all of them are outdoor insects.

• No-see-ums are biting midges. Adults are only 1 to 2 mm long, and only the females bite, says the University of Florida. The same guide warns that regular window screens don’t keep them out. They are worst at dawn and dusk near marshes, mud, and shorelines.
• Buffalo gnats are black flies. They are dark with an arched back, and they breed in flowing water like streams and rivers. Only the females bite, and they feed during the day. Purdue University counts 255 black fly species in North America and notes that black flies don’t come into buildings to bite.

If something is biting you in the yard and you never get a good look at it, our gnat vs mosquito guide can help you sort it out.

Gnats That Swarm Your Face but Don’t Bite

• Eye gnats are shiny black or gray with yellow to orange-brown legs. They go for the moisture around eyes, noses, and cuts. They don’t break the skin. They breed in moist, sandy soil, says the University of California, and they are most common in the Southeast and Southwest.
• Non-biting midges look like mosquitoes but can’t bite. Males have fuzzy antennae. They rise in clouds near ponds and lakes and pile up at porch lights at night.
• Gall midges are tiny, delicate gnats that live on plants. They aren’t house pests, but a few fly in toward lights.

Gnat Behavior and Biology

Gnats go through four life stages: egg, larva, pupa, and adult. How long each stage lasts depends on the species and weather. Fungus gnats can go from egg to adult in about 17 days at 75°F, and three to four weeks is normal in a cooler room.

Female gnats lay eggs where food and moisture are easy for larvae to find. Fungus gnats lay eggs in wet soil with organic matter. Eye gnats and buffalo gnats lay eggs near sandy soil or flowing water. A single fungus gnat can lay up to 200 eggs. Gnats don’t breed in a glass of clean water the way mosquitoes do. They need wet soil, drain slime, mud, or a stream.

The larva stage is the longest part of a gnat’s life. Fungus gnat larvae spend about two weeks eating fungi, rotting plant matter, and sometimes plant roots in the top few inches of soil. Buffalo gnat larvae grow in streams, holding onto rocks while feeding. Where larvae grow matters a lot for how big a population gets.

Adult fungus gnats live only about 7 to 10 days. During this time, they mate and females look for places to lay eggs. Most gnats are weak fliers and stay close to where they breed. They are often drawn to lights and may gather near windows during the day.

What Attracts Gnats

Knowing what draws gnats into homes helps you control them:

• Moisture: Overwatered plants, leaky pipes, damp basements, and standing water attract many gnats
• Rotting Matter: Decaying plants, compost, and spoiling food give gnats places to breed and food for larvae
• Fermenting Foods: Ripe and rotting fruit, spilled drinks, and recycling bins attract fruit flies and gnats
• Body Heat and Breath: Biting gnats and eye gnats are drawn to people by body heat and the carbon dioxide we breathe out
• Light: Many gnats are drawn to light and enter homes through open doors and windows at night
• Fungi and Mold: Fungus gnats eat fungi and are drawn to moldy areas in soil or rotting debris

How to Get Rid of Gnats at Home

Gnat control comes down to finding where the larvae live and taking that away. Spraying the adults you can see does very little, because new ones hatch from the source every day. Gnats and other small flies are not covered under our pest control plans, and most gnat problems are ones a homeowner can fix without us. Here is what works. For a full walk-through, see our guide on how to get rid of gnats.

When Gnats Keep Coming Back

If the gnats return after you have cleaned up, the source is still there and it is hidden. Daren, one of our registered technicians, says the house he is proudest of figuring out was a drain fly house. The flies went on and on, and everyone had a theory. He kept coming back to the double-pane windows, because he figured moisture was trapped inside them. He was right. When the family later renovated and pulled the windows, there was a solid line of larvae behind them.

Most homes are not that hard, but the lesson holds. Check every place that stays wet. That means the saucer under each plant, the drain in the basement floor, the pan under the fridge, the garbage disposal, and any window or wall with a moisture problem.

Source Elimination

The best way to manage gnats is to remove the conditions they need to breed:

• Water Plants Less: Let the top inch or two of soil dry between waterings. This simple step makes soil bad for fungus gnat eggs and larvae.
• Clean Your Drains: Remove buildup in sink and floor drains where drain flies and some gnats breed. Use drain cleaners or scrub pipes to remove the slimy film that larvae eat.
• Handle Produce Right: Store ripe fruit in the fridge. Throw away overripe produce quickly. Keep compost bins sealed or outside.
• Cut Down Moisture: Fix leaky faucets and pipes. Add fans to damp areas. Remove standing water from saucers, trays, and containers.

Trapping and Monitoring

Traps can reduce adult gnat numbers and help you find where they are breeding:

• Yellow Sticky Traps: These catch fungus gnats and other small flies. Place them flat on soil or upright near plants to catch adults and track how many you have.
• Apple Cider Vinegar Traps: Put apple cider vinegar in a shallow dish with a drop of dish soap. This mix attracts and drowns fruit flies and gnats. The soap breaks the water surface so they sink.
• Wine Traps: Like vinegar traps, old wine draws gnats looking for fermenting smells.
• Light Traps: Electric traps with UV light attract many flying bugs including gnats. They work best in dark areas away from other lights.

Biological Controls

Several natural control methods target gnat larvae:

• Bti (Bacillus thuringiensis israelensis): This natural soil bacteria makes toxins that kill fly larvae. It is sold as mosquito bits or dunks. Soak it in water and pour the water into the soil to kill fungus gnat larvae. Follow the label for how much to use.
• Parasitic Nematodes: These tiny worms (Steinernema feltiae) attack and kill fungus gnat larvae in soil. They hunt for larvae and keep working as long as soil stays moist.
• Predatory Mites and Beetles: Certain mites and beetles eat gnat eggs and larvae. Commercial greenhouses often use these for control.

Environmental Management

Keeping gnats out and making your home less inviting to them cuts down on numbers:

• Screen Windows and Doors: Fine mesh screens stop many gnats from getting inside. Fix any tears or gaps.
• Reduce Outdoor Lighting: Use fewer lights near doors, or switch to yellow bulbs that attract fewer bugs.
• Improve Drainage: Make sure plant pots drain well. Do not let water sit in saucers.
• Store Soil Right: Keep extra potting soil in sealed bags or bins so gnats cannot breed in it.

Prevention Strategies

Stopping gnat problems before they start is easier than getting rid of them later:

• Check new plants for gnats before bringing them inside. Keep them separate for a few weeks.
• Use potting mixes and pots that drain well.
• Do not overwater plants. Let the soil surface dry between waterings.
• Store fruit and vegetables properly. Throw away overripe items right away.
• Keep drains clean and free of buildup.
• Empty and wash garbage cans often.
• Rinse bottles and cans before putting them in recycling.

Related Resources

Not sure which type of gnat you are dealing with? These guides can help you identify and manage specific gnat problems:

• Gnats vs Fruit Flies: Learn how to tell gnats apart from fruit flies based on appearance, behavior, and breeding sites.
• Drain Flies vs Gnats: Understand the key differences between drain flies and gnats so you choose the right treatment.
• Gnat vs Mosquito: Find out whether the biting pests in your yard are gnats or mosquitoes.
• Fungus Gnats vs Drain Flies: A side-by-side comparison of two commonly confused indoor pests.
• How to Get Rid of Gnats: Step-by-step help once you know which gnat you have.

References

• Fungus Gnats Management Guidelines - University of California
• Fungus Gnats and Shore Flies - Purdue Extension
• Fungus Gnats as Houseplant Pests - Colorado State University Extension
• Small Flies - University of Kentucky Entomology
• Phorid Flies - NC State Extension
• Eye Gnats - University of California Statewide Pest Program
• Gnats - Clemson Cooperative Extension
• Biting Midges, No-See-Ums - University of Florida IFAS
• Black Flies - Purdue University Medical Entomology