Size first. The flying insects that end up indoors split cleanly into tiny (under 5 mm), medium (house-fly sized) and large, and within each size the room tells you the rest. The two that matter for your health or your food are at the end.
Tiny: under 5 mm
Fruit flies. Tan body, red eyes, slow drifting flight over anything fermenting. They arrive with fruit and breed in it, in the bin, and in the film at the bottom of an empty wine bottle. Card #132. Fix: remove the fermenting thing; a dish of vinegar with a drop of soap catches the stragglers.
Fungus gnats. Black, delicate, mosquito-shaped, weak fliers that walk on the soil of houseplants and bump into your screen. The larvae live in wet potting mix. Fix: let the top of the soil dry out between waterings; yellow sticky cards show you the scale of it.
Drain flies. Fuzzy, grey, holding their wings like a tiny moth, sitting still on bathroom tiles. They breed in the slime inside drains and overflow pipes. Fix: a stiff brush down the drain and hot water. Bleach poured in does little because the larvae live in the film, not the water.
Whiteflies. Pure white, moth-like, rising in a cloud when you touch a houseplant. A plant pest, never a people problem. Fix: rinse the leaves, or accept that the plant is their home.
Flying ants and termite swarmers. A sudden crowd of winged insects on one warm day, usually spring or late summer. Ants have a pinched waist and wings of two different sizes; termites have a straight body and four equal wings. Flying ants are a garden colony’s founders and harmless. Termite swarmers indoors mean a colony in the building: see card #145 and get it looked at.
Medium: about the size of a house fly
House fly. Grey, four dark stripes on the back, comes in through the door and heads for food. Card #124. A few in summer is normal. Many, day after day, means a breeding site nearby: an uncollected bin, pet waste, compost too close to a window.
Bluebottle and greenbottle. Metallic blue or green, loud, bumping at the glass. Card #127. They lay on meat and on dead animals. One in winter, indoors, often means a mouse or bird has died in a wall or loft space; the flies find it before you do.
Cluster flies. Slightly larger than a house fly, dull, sluggish, appearing in numbers at upstairs windows on sunny winter days. They overwinter in lofts and do not breed indoors. A vacuum is the whole answer.
Mosquitoes. Small, thin, a whine near your ear at night, landing on skin. The common house mosquito breeds in any standing water: a blocked gutter, a saucer under a pot, a paddling pool. Tip the water out and the numbers drop within two weeks.
Wasps and bees. A common wasp inside in August is a forager after sugar; a bee is usually lost. Open the window and turn off the light behind it. Repeated wasps from the same spot, or a steady stream in and out of a vent, is a nest.
Large: you noticed it from across the room
Crane fly. Long spindly legs, slow bobbing flight, bumps around the lampshade. Often called a giant mosquito, which it is not: it cannot bite, and it will lose a leg if you grab it. Card #129. Cup it and put it out.
Outdoor moths. Big, dusty, drawn to the light through an open window on a warm night. They do not eat clothes; the clothes-eating moths are small and avoid light. Look at the night shift set in the Field Guide if you want a name, then let it out in the morning.
Autumn visitors. Ladybirds, stink bugs and boxelder bugs fly to sunny walls in October and slip inside to spend the winter. The Asian lady beetle and the brown marmorated stink bug are the usual ones. They eat nothing indoors and leave in spring. Sweep, jar, outside.
Lacewings. Pale green, delicate, gold eyes, at the window in summer. One of the best aphid-eaters in the garden and completely harmless. Card #135.
The moth question
Two indoor moths are worth telling apart from the visitors:
- Clothes moths are small (under 1 cm), plain golden-brown, and scuttle away from light rather than flying to it. You find them in wardrobes and under furniture. The larvae eat wool, silk and feathers.
- Pantry moths are small, grey-brown with a copper band, and fly out of the cereal cupboard. The larvae leave webbing in flour, nuts and dried fruit.
Both are fixed at the source: the infested garment or packet. Traps tell you whether they are still around.
Front desk note: killing the adult flies is the least effective thing you can do. Every one of these has a nursery somewhere, and the nursery is what you are looking for.
The two that matter
- Mosquitoes, because they bite and, in some places, carry disease. Standing water is the whole story.
- Termite swarmers, because they are the only flying insect in this list that tells you something about the building.
Everything else is a wanderer, a nuisance, or a plant problem. If you want a name for the one on your ceiling right now, a photo in the identifier will do it, and the Field Guide has each species’ season and safety notes.
Questions
What are the tiny flying bugs in my house?
Almost always one of three: fruit flies (tan, red eyes, over fruit and bins), fungus gnats (black, delicate, around houseplants) or drain flies (fuzzy, moth-shaped, on bathroom tiles). Each has a different breeding site, and removing the site removes the flies.
How do I get rid of small flies in the kitchen?
Find what they are breeding in. Fruit flies: overripe fruit, the recycling, the bin. Fungus gnats: wet potting soil, so let plants dry out between waterings. Drain flies: the biofilm inside a drain, which needs a brush, not bleach. Traps catch adults but do not stop the next generation.
Is it a mosquito or a crane fly?
A crane fly is much bigger, with legs that fall off if you touch it and no interest in you at all. Mosquitoes are small, whine, and land on skin. Crane flies do not bite.
Why are there moths in my house?
Outdoor moths come to lights through open windows and leave on their own. Small golden-brown moths that scuttle in wardrobes are clothes moths; small grey-brown ones in the kitchen are pantry moths. The larvae of those two are the ones doing damage, so look for the source packet or garment.
