Bugs You See Indoors in Winter
These bugs stay active indoors through the cold months. This guide covers 27 of them.
Quick list
- Black Widow Spider
- Brown Recluse Spider
- Bed Bug
- Cat Flea
- Head Louse
- American Cockroach
- Asian Lady Beetle
- Boxelder Bug
- Brown Marmorated Stink Bug
- Brown-Banded Cockroach
- Cigarette Beetle
- Confused Flour Beetle
- Drain Fly
- Drugstore Beetle
- Fungus Gnat
- German Cockroach
- House Centipede
- Indian Meal Moth
- Pharaoh Ant
- Rice Weevil
- Silverfish
- Southern House Spider
- Webbing Clothes Moth
- Western Conifer Seed Bug
- Booklouse
- Cellar Spider
- Common House Spider
How to narrow it down
Narrow it down with three quick checks. Count the legs: insects have six, spiders and ticks have eight, and centipedes and millipedes have many more. Check for wings, even folded ones. Then compare size against a coin: a US penny is 19 mm across. Our bug identifier tool does this filtering for you.
The 27 bugs
Black Widow Spider
Black Widow SpiderLatrodectus mactansA shiny black spider with a red hourglass on the underside of its round abdomen. It builds messy, tangled webs in woodpiles, sheds, meter boxes and outdoor furniture.
Tell-tale sign: Glossy black, globe-shaped abdomen. Risk: Females have venom that can cause severe muscle pain and cramps; seek medical care after a bite.
Brown Recluse Spider
Brown Recluse SpiderLoxosceles reclusaA tan to brown spider with a dark violin-shaped mark on its back and only six eyes. It hides in boxes, closets and unused clothing in the south-central US.
Tell-tale sign: Dark violin-shaped mark pointing toward the abdomen. Risk: Most bites are mild, but some cause a spreading wound that needs medical care.
Bed Bug
Bed BugCimex lectulariusA flat, oval, apple-seed-sized insect that hides in mattress seams, bed frames and furniture and feeds on human blood at night. Infestations spread through luggage, used furniture and shared walls.
Tell-tale sign: Flat, oval, reddish-brown body without wings. Risk: Bed bug bites itch and cause stress and sleep loss, but bed bugs are not known to spread disease.
Cat Flea
Cat FleaCtenocephalides felisThe most common flea on both cats and dogs, a tiny, flattened, dark insect that jumps huge distances. Eggs drop off pets into carpets and bedding.
Tell-tale sign: Tiny, reddish-brown to black body flattened side to side. Risk: Flea bites itch, can cause allergic dermatitis in pets, and fleas can pass tapeworms.
Head Louse
Head LousePediculus humanus capitisA tiny, wingless insect that lives only on the human scalp and feeds on blood. Its eggs, called nits, are glued firmly to hair near the scalp.
Tell-tale sign: Sesame-seed-size tan or grayish insect on hair. Risk: Head lice are itchy but don't spread disease; they spread mainly by head-to-head contact.
American Cockroach
American CockroachPeriplaneta americanaThe largest common house cockroach, a reddish-brown roach that lives in sewers, basements and steam tunnels. It can fly short distances in warm weather.
Tell-tale sign: Large reddish-brown body up to two inches long. Risk: American cockroaches can spread bacteria to food and trigger allergies and asthma.
Asian Lady Beetle
Asian Lady BeetleHarmonia axyridisAn imported lady beetle that ranges from pale orange to red with anywhere from zero to 19 spots. In fall it gathers in large numbers on sunny walls and slips indoors to spend the winter.
Tell-tale sign: Orange to red dome-shaped body with a variable number of spots. Risk: They can give a mild pinch and release a yellow, smelly fluid that stains, but they carry no disease.
Boxelder Bug
Boxelder BugBoisea trivittataA black bug with red-orange lines on its back that feeds on the seeds of boxelder and maple trees. Large groups sun themselves on warm walls in fall before crawling inside.
Tell-tale sign: Black body with three red lines on the thorax. Risk: Boxelder bugs rarely bite and are harmless, but their droppings can stain curtains.
Brown Marmorated Stink Bug
Brown Marmorated Stink BugHalyomorpha halysA shield-shaped, mottled brown bug that invades homes in fall to overwinter and feeds on fruit and vegetables in summer. It releases a sharp odor when disturbed or crushed.
Tell-tale sign: Shield-shaped, marbled brown body. Risk: Stink bugs don't bite or sting people; they are a household and crop nuisance.
Brown-Banded Cockroach
Brown-Banded CockroachSupella longipalpaA small cockroach with two light bands across its back that prefers warm, dry spots high in rooms. It hides behind picture frames, in electronics and inside furniture.
Tell-tale sign: Two pale yellow bands across the wings and abdomen. Risk: They carry bacteria and allergens like other cockroaches but are not known to bite.
Cigarette Beetle
Cigarette BeetleLasioderma serricorneA tiny, humpbacked, reddish-brown beetle that infests tobacco, spices, dried flowers, cereals and pet food. Adults are strong fliers and are often found near windows.
Tell-tale sign: Rounded, humped body with smooth, ungrooved wing covers. Risk: Cigarette beetles do not bite; they contaminate and damage stored products.
Confused Flour Beetle
Confused Flour BeetleTribolium confusumA flat, slender, reddish-brown beetle common in flour, cake mixes, cereals and other milled foods. Heavy infestations leave a grayish tint and a sharp, unpleasant smell.
Tell-tale sign: Flat, elongated reddish-brown body. Risk: They don't bite or sting; infested flour tastes and smells bad.
Drain Fly
Drain FlyClogmia albipunctataA small, fuzzy, moth-like fly that rests on bathroom walls near sinks, tubs and floor drains. Its larvae live in the slimy film inside drains.
Tell-tale sign: Fuzzy, gray, leaf-shaped wings held roof-like over the body. Risk: Drain flies don't bite and aren't known to spread disease in homes.
Drugstore Beetle
Drugstore BeetleStegobium paniceumA small, reddish-brown pantry beetle with rows of fine grooves along its wing covers. It infests dried foods, spices, pet food, and even books and medicines.
Tell-tale sign: Oval, reddish-brown body with lengthwise grooves. Risk: Drugstore beetles don't bite or spread disease, but they ruin stored food.
Fungus Gnat
Fungus GnatBradysia spp.A tiny, dark, mosquito-like fly that hovers around houseplants and windows. Its larvae live in moist potting soil and feed on fungi and roots.
Tell-tale sign: Delicate dark body with long legs and antennae. Risk: Fungus gnats don't bite; larvae can damage seedlings and young roots.
German Cockroach
German CockroachBlattella germanicaA small, light-brown cockroach that breeds rapidly in kitchens and bathrooms, especially in apartments and restaurants. Females carry their egg case until it is ready to hatch.
Tell-tale sign: Light tan to brown body about half an inch long. Risk: German cockroaches contaminate food, and their droppings and shed skins are a major asthma trigger.
House Centipede
House CentipedeScutigera coleoptrataA fast, yellowish-gray centipede with 15 pairs of very long legs that races across floors and walls at night. It hunts silverfish, cockroaches and spiders.
Tell-tale sign: Fifteen pairs of long, banded legs. Risk: House centipedes rarely bite; a bite feels like a mild bee sting.
Indian Meal Moth
Indian Meal MothPlodia interpunctellaThe most common pantry moth, with wings that are pale gray near the body and coppery bronze at the tips. Larvae spin silk webbing in grains, nuts, cereal, birdseed and dried fruit.
Tell-tale sign: Two-toned wings, cream at the base and rusty bronze at the tips. Risk: Pantry moths don't bite and aren't toxic; infested food should be thrown away.
Pharaoh Ant
Pharaoh AntMonomorium pharaonisA tiny, pale yellow ant that nests in warm, hidden spots inside walls, cabinets and appliances. Colonies split into new nests when disturbed, which makes them hard to control.
Tell-tale sign: Very small, light yellow to amber body with a darker abdomen. Risk: They don't bite, but in hospitals and kitchens they can carry bacteria onto clean surfaces.
Rice Weevil
Rice WeevilSitophilus oryzaeA small, dark weevil with a long snout and four faint reddish spots on its back. Females chew holes in whole grains such as rice, wheat and corn and lay an egg inside each kernel.
Tell-tale sign: Long, narrow snout extending from the head. Risk: Rice weevils cannot bite people and are not harmful if accidentally eaten, but they spoil grain.
Silverfish
SilverfishLepisma saccharinaA wingless, carrot-shaped insect covered in silvery scales that moves with a fish-like wiggle. It eats paper, glue, starches and fabrics in damp areas.
Tell-tale sign: Silvery-gray, teardrop-shaped, scaly body. Risk: Silverfish don't bite; they damage books, wallpaper and stored papers.
Southern House Spider
Southern House SpiderKukulcania hibernalisA velvety, dark gray to brown spider of the southern US whose males look like brown recluses. Females build radiating, lint-like webs around cracks in walls and windows.
Tell-tale sign: Velvety, uniformly dark females with a small head. Risk: Southern house spiders rarely bite and are not medically significant.
Webbing Clothes Moth
Webbing Clothes MothTineola bisselliellaA small, golden-buff moth whose larvae eat wool, silk, fur, feathers and cashmere. Adults avoid light and are more often found in closets than flying around lamps.
Tell-tale sign: Small, shiny golden-tan wings without spots. Risk: Clothes moths don't bite people; larvae damage natural-fiber fabrics.
Western Conifer Seed Bug
Western Conifer Seed BugLeptoglossus occidentalisA long, brown bug with flattened, leaf-like expansions on its hind legs. It feeds on pine cones in summer and wanders indoors in fall, buzzing loudly when it flies.
Tell-tale sign: Leaf-shaped flat widenings on the hind legs. Risk: Western conifer seed bugs don't bite or sting; they may release a pine-like odor.
Booklouse
BooklouseLiposcelis spp.A tiny, soft, pale insect that feeds on microscopic mold growing on paper, cardboard and stored food. It thrives in humid rooms and new construction.
Tell-tale sign: Very small, pale, wingless body. Risk: Booklice don't bite and aren't true lice; they indicate high humidity and mold.
Cellar Spider
Cellar SpiderPholcus phalangioidesA pale, delicate spider with extremely long, thin legs that hangs upside down in loose webs in basements and ceiling corners. When disturbed, it vibrates rapidly in its web.
Tell-tale sign: Tiny, peanut-shaped body with very long, hair-thin legs. Risk: Cellar spiders are harmless to people; the myth that they are deadly but can't bite is false.
Common House Spider
Common House SpiderParasteatoda tepidariorumA small, brownish spider that builds tangled cobwebs in corners, windows and basements. It is the web-builder most often seen inside North American homes.
Tell-tale sign: Round, mottled brown abdomen with chevron markings. Risk: Common house spiders are harmless and help catch flies and other indoor pests.
Which ones should you worry about?
5 of the 27 bugs in this guide can bite or sting. The ones to take seriously are black widow spider and brown recluse spider. The rest are harmless or simply a nuisance.
Frequently asked questions
What is the most common one?
Among the bugs in this guide, the black widow spider and brown recluse spider are the ones people ask about most.
Which of these are dangerous?
Black Widow Spider and Brown Recluse Spider can be medically significant.
How can I identify a bug I found?
Use the free bug identifier tool: choose the number of legs, wings, main color, size and where you found it, and it will list the closest matches.