Sorted by where you are likely to meet it. Each plate carries the species, the adult size, what it means for the building, and the photographer — because a photograph you cannot attribute is a photograph you cannot trust.
If it is small, brown, and you found it near a bed, go straight to the look-alikes page. That one distinction is worth more than everything else here.
Excavates galleries in damp or previously wet wood — it does not eat it. The tell is coarse sawdust with insect parts in it under a sill or a window. Big, black, and out at night.
Original uploader was Muéro at en.wikipedia · Public domain · source
The small dark ant coming up through a crack in a slab or a driveway seam. Trails to whatever is sweet or greasy. Structurally harmless and easy to stop at the source.
Bradley Rentz · CC BY-SA 4.0 · source
Pale, soft, and it genuinely eats the wood. Present in Michigan but far less common than carpenter ants — which is exactly why the two get confused. Mud tubes on a foundation wall are the giveaway.
Public domain · source
Flat and oval when unfed, rounder and darker after a meal. Six legs, no wings, and it does not jump or fly. Found in seams, not in carpet. Never a hygiene problem — it is a travel problem.
Content Providers(s): CDC/ Harvard University, Dr. Gary Alpert; Dr. Harold Harlan; Richard · Public domain · source
Mottled, rounded and hard-shelled, with a domed back. Mistaken for a bed bug more than anything else on this page, and the difference decides whether you spend $200 or $1,800.
Didier Descouens · CC BY-SA 4.0 · source
Two dark stripes behind the head. Breeds indoors year-round and is a documented asthma trigger. Gets in on cardboard, groceries and secondhand appliances, not through the door.
Clemson University - USDA Cooperative Extension Slide Series, · CC BY 3.0 us · source
Teardrop, metallic, three tails, moves like a fish. Eats starch — paper, book bindings, wallpaper paste. Where it appears tells you where the humidity is, which is the actual problem.
Aiwok · CC BY-SA 3.0 · source
Fifteen pairs of long legs and genuine speed. The most alarming thing most people ever see indoors and one of the least harmful — it hunts the things you would rather not have. It means the basement is damp.
Didier Descouens · CC BY-SA 4.0 · source
Tangled cobwebs in ceiling corners and window frames, with pale round egg sacs. Michigan has no aggressive house spider worth fearing. Removing the webs removes the spider.
Adrian Tync · CC BY-SA 4.0 · source
Black with red-orange lines, on a sunny south or west wall in October. Comes in to overwinter, does not feed or breed indoors, and does not bite. Sealing beats spraying every time.
Rhododendrites · CC BY-SA 4.0 · source
Shield-shaped, mottled brown, with pale bands on the antennae. Same October wall, same reason. Vacuum rather than crush — the name is not decorative.
Hectonichus · CC BY-SA 4.0 · source
Slow, sluggish flies at an upstairs window in the first warm week of spring. They overwintered in the attic and are trying to get out. Not a sanitation problem and not from a drain.
Richard Bartz, Munich aka Makro Freak · CC BY-SA 2.5 · source
Bright yellow and black, hairless, and aggressive near the nest — which is usually underground or inside a wall void. Peaks in August and September. Do not seal the entrance with the nest still active.
jonsense · CC BY 4.0 · source
The gray paper football in a tree or under an eave. Defends a wide radius and does not need provocation. If it is above head height and away from the door, leaving it until the first hard frost is a legitimate option.
The High Fin Sperm Whale · CC BY-SA 3.0 · source
Flattened side to side so it moves through hair, and it jumps. Bites cluster around ankles. The animal is treated by a veterinarian and the house is treated by us — doing only one of those is why it comes back.
Katja ZSM · CC BY-SA 3.0 · source
Eight legs, so not an insect at all. Picked up in long grass and edges rather than indoors. Save any tick you remove in a bag — if you get sick, what it was matters to your doctor.
Jerry Kirkhart from Los Osos, Calif. · CC BY 2.0 · sourceHalf the photographs we get cannot be worked with, and it is nearly always the same three problems. Two minutes of care here saves a visit.
Put something next to it for scale. A coin, a key, the tip of a pen. Size is the first thing that gets ruled in or out and a photograph has no size.
Get the light on it, not behind it. Phone flash on, from the side if you can. A silhouette is not identifiable.
Take it from directly above, then from the side. The waist, the antennae and the wing length are the diagnostic characters, and you cannot see all three from one angle.
Clear tape over the specimen on a white index card works better than almost anything else, and it keeps the animal intact if we need to see it in person.
It is general entomology written for a homeowner, and it is good enough to answer most kitchen-table arguments and to stop somebody selling you a treatment you do not need.
It is not a determination. Several of these are separated by characters you need a hand lens for, and one of them — carpenter ant against termite — is worth getting properly wrong-proofed by somebody standing in your basement.
Send us a photograph. If it is one of the easy ones we will tell you for nothing and you will not need us at all.
Three are public-domain images from the CDC and USDA. The rest are Creative Commons, and the photographer’s name and the license link sit at the bottom of each plate because that is what those licenses require — not as a courtesy, as a condition of use. The credit is generated from the image metadata at build time rather than typed by hand, so it cannot quietly drift away from the picture it belongs to.
A real company replacing these with its own photographs inherits something better: pictures of the actual animals it found in actual houses in this actual county.