Insects ExplainedIdentification, Biology & Pest Management
Found a bug? Use the identification finder

Identify an Insect

Tell the finder where you saw the insect, its size, color, shape and behavior. It suggests likely matches from the insects most often found in and around US homes.

Insect finder

The interactive finder needs JavaScript. The guides below cover the same insects, sorted by where they turn up and what they look like.

These are suggestions, not a diagnosis. Many small insects look alike, and size and color vary with age. Check the guide for each match, and if the insect could damage your home or health, confirm it with a sample sent to your county extension office or a licensed professional.

Identify by where you found it

Identify by how it looks

Commonly confused insects

Termite swarmer or winged ant?

Carpet beetle or bed bug?

Cat flea or bed bug?

Honey bee or yellowjacket?

Getting a good identification

Most wrong identifications come from guessing at size and skipping the location. A few habits make any guide, including this one, far more reliable.

  • Measure it. Lay the insect next to a ruler or a coin. A US penny is 19 mm across; a grain of rice is about 6 mm long.
  • Photograph the top and the side. Antennae, the waist, wing length and leg shape separate many look-alikes, and a phone held a few inches away usually captures them.
  • Note where and when. The room, the time of year, and whether you found one or many narrow the list more than color does.
  • Keep a specimen. Clear tape, a sealed plastic bag or a small jar with rubbing alcohol preserves an insect for a closer look. County extension offices identify insects for residents, often at little or no cost.
  • Look for evidence, not just insects. Droppings, shed skins, egg cases, frass, holes and webbing often point to the culprit before you see a live one.

The finder covers the insects most often found in and around houses. It does not cover every insect. For broader groups, start with the orders of insects and external anatomy.

Insects in the finder

InsectSizeUsually foundLook for
German cockroach 10 to 25 mm kitchen, bathroom, pantry or food Light brown with two dark stripes behind the head. Breeds indoors.
American cockroach over 25 mm basement, bathroom, kitchen, outdoors Large and reddish brown with a pale band around the shield behind the head.
Oriental cockroach 10 to 25 mm, over 25 mm basement, bathroom, outdoors Shiny, very dark roach of cool damp places. Often called a water bug.
Cockroach nymph 2 to 5 mm, 5 to 10 mm kitchen, bathroom, pantry or food Wingless young roaches. Several sizes together point to an infestation.
Termite workers 2 to 5 mm in or near wood, basement, outdoors Pale, soft, eyeless. Found inside wood or mud tubes, rarely in the open.
Termite swarmers 5 to 10 mm windows, basement, bed or bedroom, kitchen, in or near wood, outdoors Straight antennae, thick waist, four equal wings that drop off. Often near windows in spring.
House ants under 2 mm, 2 to 5 mm, 5 to 10 mm kitchen, bathroom, pantry or food, outdoors Elbowed antennae and a pinched waist. Trails lead back to the colony.
Carpenter ants 5 to 10 mm, 10 to 25 mm in or near wood, kitchen, outdoors, attic Large ants that hollow out damp wood and leave coarse sawdust.
Winged ants 5 to 10 mm, 10 to 25 mm windows, kitchen, outdoors, basement Elbowed antennae, pinched waist, front wings longer than hind wings.
Bed bugs under 2 mm, 2 to 5 mm, 5 to 10 mm bed or bedroom Flat, oval, wingless. Hide in mattress seams and bed frames; bite at night.
Fleas under 2 mm, 2 to 5 mm on pets or pet bedding, bed or bedroom, outdoors Tiny, flattened side to side, and jumps well. Bites often land on ankles.
Carpet beetle adults under 2 mm, 2 to 5 mm windows, bed or bedroom, clothes, rugs, closets, attic Tiny rounded beetles, mottled or solid black, often at sunny windows in spring.
Carpet beetle larvae 2 to 5 mm, 5 to 10 mm clothes, rugs, closets, bed or bedroom, pantry or food, basement Bristly, banded, carrot-shaped larvae. Shed skins are a common find.
Drugstore and cigarette beetles under 2 mm, 2 to 5 mm pantry or food, kitchen, windows Small, rounded, reddish brown. Infest spices, flour, dry pet food.
Sawtoothed grain beetle 2 to 5 mm pantry or food, kitchen Very slim and flat with saw-like teeth on each side of the thorax.
Flour beetles 2 to 5 mm pantry or food, kitchen Reddish brown, slender beetles in flour and mixes.
Rice and granary weevils 2 to 5 mm pantry or food, kitchen Small beetles with a long snout. Larvae develop inside whole grains.
Spider beetles under 2 mm, 2 to 5 mm pantry or food, kitchen, basement Round, long-legged beetles that look a bit like tiny spiders.
Indian meal moth 5 to 10 mm, 10 to 25 mm pantry or food, kitchen Small moth with two-tone wings: pale near the body, coppery at the tips.
Pantry moth larvae 5 to 10 mm, 10 to 25 mm pantry or food, kitchen Pale caterpillars with webbing in food; they wander to ceilings to pupate.
Powderpost beetles 2 to 5 mm, 5 to 10 mm in or near wood, basement, attic Rarely seen. Pinholes and fine powder in wood are the usual clue.
Silverfish and firebrats 10 to 25 mm bathroom, basement, kitchen, attic Carrot-shaped, scaly, three tail filaments, quick wriggling run.
House fly 5 to 10 mm kitchen, outdoors, windows Gray fly with four dark stripes on the thorax.
Cluster flies 5 to 10 mm windows, attic, bed or bedroom Sluggish flies at sunny windows in fall and late winter.
Fruit flies under 2 mm, 2 to 5 mm kitchen, pantry or food Tiny tan flies, usually with red eyes, around ripe fruit and drains.
Drain flies under 2 mm, 2 to 5 mm bathroom, kitchen, basement Fuzzy, moth-like flies resting on walls near drains.
Fungus gnats under 2 mm, 2 to 5 mm on plants, kitchen, bed or bedroom Delicate black gnats around overwatered houseplants.
Phorid flies under 2 mm, 2 to 5 mm kitchen, bathroom, basement Humpbacked small flies that run rather than fly away. Point to decaying organic matter.
Mosquitoes 2 to 5 mm, 5 to 10 mm outdoors, bed or bedroom, basement Slender with long legs and a piercing beak. Females bite.
Yellowjackets and hornets 10 to 25 mm outdoors, attic, kitchen Smooth, yellow and black, narrow waist. Defend nests aggressively.
Paper wasps 10 to 25 mm, over 25 mm outdoors, attic, windows Long-legged wasps with open, umbrella-shaped nests under eaves.
Honey bees 10 to 25 mm outdoors, on plants Fuzzy, golden brown. Gentle away from the hive; important pollinators.
Brown marmorated stink bug 10 to 25 mm windows, attic, bed or bedroom, on plants, outdoors Shield-shaped bug that gathers indoors in fall. Smells when crushed.
Multicolored Asian lady beetle 5 to 10 mm windows, attic, on plants, outdoors Dome-shaped, orange to red, variable spots. Gathers indoors in fall and can pinch.
Ground beetles 5 to 10 mm, 10 to 25 mm basement, outdoors, kitchen Shiny dark beetles that wander in from outdoors and do not breed inside.
Aphids under 2 mm, 2 to 5 mm on plants, outdoors Soft, pear-shaped sap feeders in clusters on new growth.
Springtails under 2 mm bathroom, basement, on plants, kitchen Minute six-legged jumpers in damp spots. Harmless but signal moisture.
Booklice under 2 mm pantry or food, kitchen, basement, bathroom Pale, soft, barely visible insects that feed on mold in humid places.
Caterpillars 10 to 25 mm, over 25 mm on plants, outdoors Soft larvae with three pairs of true legs and fleshy prolegs. Some sting.