Household Bug Identification: Common House Bugs by Room

You identify a household bug fastest by where you found it and how big it is, because most indoor pests are tied to one kind of room: food, water, fabric or wood. University of Maryland Extension's household insect guide sorts bugs by how they move (flying, jumping, crawling); the lists below re-sort the same insects by room so you can start from where you are standing. Sizes are from UMD unless another source is named.

A very small beetle or moth near dry food is almost always a pantry pest. UC IPM gives these identifiers:

• Sawtoothed grain beetle: about 1/10 inch, brown and flat, with six saw-like teeth along each side of the thorax
• Cigarette and drugstore beetles: about 1/8 inch, cylindrical and uniformly light brown
• Confused and red flour beetles: about 1/7 inch
• Indianmeal moth: 1/3 to 2/5 inch long with a wingspan of about 3/5 inch; reddish-brown forewings with a coppery sheen on the outer two-thirds. Its larvae are whitish with a brown head, about 1/2 inch, and are often seen crawling up walls (UMD)
• Rice and granary weevils: 1/8 to 1/4 inch, narrow, reddish-brown to black, with a distinct snout (UMD)

Other small kitchen insects: fruit flies (tan with red eyes, near fruit and recycling bins), phorid flies (tiny and dark, breeding in decaying organic matter), indoor ants and the German cockroach (see cockroach identification).

• Drain flies: tiny (2 mm), grey, fuzzy and moth-like, near sinks and drains
• Springtails: 1/8 inch or less, grey to white, jump; bathrooms, flower pots and humid areas
• Silverfish and firebrats: about 1/2 inch, flattened, grey or tan, with three tails; boxes, cabinets, bathrooms and near the furnace
• House centipede: over 1 inch, greyish-yellow with three dark stripes and 15 pairs of long legs; UMD lists it as harmless because it eats other indoor insects
• Cave or camel crickets: over 1 inch, hump-backed, wingless and brown, in basements; they do not chirp
• Millipedes (1 inch or longer, curl up) and pill bugs and sow bugs (1/2 to 3/4 inch, grey, some roll into a ball), near ground-level doors
• Booklice: 1 to 2 mm, grey to light brown, around stored papers and books
• Oriental cockroach: dark and shiny, in floor drains and basements

• Bed bugs: 1/4 to 3/8 inch before feeding, reddish-brown, oval and wingless, dark red after feeding; UMD says they require professional control. See bed bug bites.
• Clothes moths: buff-coloured, 3/8 to 1/2 inch wingspan, in closets and bedrooms
• Carpet beetles: adults 1/4 inch or less, oval to round; larvae 1/4 inch or less, carrot-shaped and furry, in closets, bathrooms and kitchens
• Fleas: 1/16 to 1/8 inch, brownish-black, flattened side to side, strong jumpers that bite; on pets and in homes. See flea bites.

• Cluster flies: 3/8 inch, dark grey, non-metallic and sluggish, at windows and lamps in fall, winter and spring
• Multicolored lady beetles: 1/4 inch, orange to red, some with spots; UMD lists them as harmless predators of aphids
• Boxelder bugs: red and black, on the south side of houses and sometimes indoors
• Bark beetles and wood borers: emerging from firewood brought indoors
• Flying ants or termite swarmers? Termite swarmers are about 1/4 to 3/8 inch, dark, with four long wings of equal length and a fluttery flight. Flying ants have a pinched waist. Termites require professional control, so this is one identification worth getting right; see termite identification.

University of Maryland Extension's guide marks each household insect. Grouped by what to do:

• Leave them alone (harmless or beneficial): house centipedes, most spiders, multicolored lady beetles, bumblebees, honey bees, ground bees, cicada killers and mud daubers
• Nuisance pests you can usually manage yourself: pantry pests, fruit and drain flies, silverfish, springtails, millipedes, pill bugs, cluster flies, boxelder bugs
• Professional control or assessment: bed bugs and termites (control), old house borers and powderpost beetles (assessment)

Carpenter ants and carpenter bees nest in wood but do not eat it, according to UMD; carpenter ants leave coarse sawdust near damaged wood.

UC IPM's advice is short and does not involve spraying:

• Find and throw away the infested package; pantry pests usually arrive in one
• Store dry food in containers with tight-fitting lids, not plastic bags
• Keep rarely used items in the freezer if possible
• Use pheromone traps to monitor moths
• Do not use insecticides; UC IPM says they are not recommended for pantry pests

Development is fast in warm weather: UC IPM gives three to four weeks from egg to adult for the sawtoothed grain beetle in summer and about six weeks for flour, cigarette and drugstore beetles, which is why one forgotten bag can seed a whole cupboard.

Photograph it and the app identifies it; the bug ID guide covers the free options and how to take a photo that works. For anything that could mean structural damage or a bed bug problem, UMD's advice is to submit photos and questions to Ask Extension, because proper identification is the first step before managing any pest.

Research and drafting for this page used AI assistance. Every figure, date and quotation was then checked line by line against the sources listed at the bottom of the page, each of which was opened while writing. Nothing here is a diagnosis. If a bite, sting or contact with an insect is followed by trouble breathing, swelling of the face or throat, spreading redness, fever or any symptom that worries you, get medical care; in the United States Poison Help (1-800-222-1222) is free and open 24 hours a day.