What Are These Tiny Bugs?
By Marcus Ellery, Pest Control Editor · Updated October 2026 · General information, not an identification
Most small bugs people find indoors fall into a short list, and three things narrow it fast: how big it is, what it looks like up close and which room it turned up in. The table below puts the size and description that EPA and university extension services publish for each one side by side. It is a starting point for matching a specimen, not a verdict; each row links to a full guide with the source’s own advice and the point where it says to call a professional.
Side by side
| Insect | Size | Look | Usually found |
|---|---|---|---|
| Clover mite | Size of a printed period | Reddish-brown, long front legs, red smear when crushed | Sunny windowsills, spring and fall |
| Boxelder bug nymph | About 1.3 mm when newly hatched | Bright red abdomen, black legs | Sunny exterior walls in fall |
| Drain fly | 1/16 to 1/4 inch | Fuzzy, moth-like wings, gray-brown to black | Bathroom walls near drains |
| Springtail | 1/16 to 1/8 inch | Slender, mostly dark, jumps | Damp grout, leaks, condensation |
| Booklouse | 1 to 2 mm | Pale to gray, wingless | Humid rooms, moldy paper or paste |
| Silverfish | About 1/2 inch, up to 3/4 | Shiny silver-gray, two long antennae | Bathrooms and damp rooms at night |
| Phorid fly | About 1/8 inch | Dark, humpbacked, runs in bursts | Drains, disposals, food debris |
| Black carpet beetle | 2.5 to 5 mm | Dull black, oval | Baseboards, little-used drawers |
| Rice weevil | About 1/8 inch | Black snout beetle, four faint spots | Rice and whole grains |
| Indianmeal moth | A third to two-fifths of an inch (adult) | Reddish-brown wing tips | Kitchen at night, webbing in food |
| Bed bug | 5 to 7 mm, apple-seed size | Flat, oval, brown; cannot fly | Mattress seams, bed frame |
| Cat flea | 1/16 to 1/8 inch | Brownish-black, jumps | Pet bedding, carpet |
| Odorous house ant | About 1/8 inch | Dark brown to black, smells when crushed | Trails to sweets in the kitchen |
Guides by where you found them
No bug in sight, but something is there
Some of the most useful clues are signs rather than insects. These guides cover what the sources say each one can point to.
Getting a real identification
Most state Cooperative Extension services, run through land-grant universities, will identify an insect from a specimen or a clear photo, often free or for a small fee. Some university labs, such as Cornell’s Insect Diagnostic Laboratory, take public submissions directly. Find your state’s land-grant university through the USDA NIFA land-grant university directory. To check that a pest control company is licensed, the NPIC directory of state pesticide regulatory agencies lists the agency in each state that certifies applicators. Cornell’s lab is at cals.cornell.edu.
Frequently asked questions
How do I find out what a tiny bug is for certain?
Catch one whole, in a sealed bag or a small container, or take a sharp photo next to a coin. State Cooperative Extension services identify specimens, and some university labs such as Cornell’s Insect Diagnostic Laboratory take submissions from the public. The NIFA land-grant directory linked on this page leads to your state’s service.
Which of these bugs bite?
Of the insects on this page, bed bugs and fleas bite people, and CSU Extension says bat bugs do too. MU Extension says clover mites do not bite, and UMaine Extension says booklice do not. If you are getting bites and the insect does not match, get it identified.
Do I need an exterminator for small household bugs?
Often not first. For pantry pests UC IPM says insecticides are not recommended, for springtails UMN Extension says moisture control is the most effective option, and for drain flies the extension sources point to scrubbing drains. Each guide lists the point at which its sources say to bring in a licensed professional.
Sizes and descriptions are summarized from the agency and university pages linked in each row; check the linked page for the full description. This page is general information, not a pest identification. PestCost is not affiliated with EPA, CDC, NPIC, USDA or any university cited. Spotted an error? Send a correction.