When a technician walks into a Detroit apartment on a bed bug call, the bed doesn’t get pulled apart in the first minute. Nobody flips a mattress. Nobody hauls a dresser across the room. The first ten minutes are almost entirely visual — standing in one place, looking at specific surfaces in a specific order, and reading what’s already there.
That’s deliberate. Moving furniture before you’ve read the room destroys the evidence trail. Crushed stains smear, shed skins get knocked into carpet, and the pattern that tells you where the population is centered disappears.
So here’s the walkthrough, in the order a tech actually does it. Every one of these signs of bed bugs is spottable tonight, with a phone flashlight, without moving a thing.
A tech works from the sleeper outward, because bed bugs feed on a schedule and travel a short distance. The evidence is densest within about six feet of where someone sleeps, and it thins out as you move away. Reading that gradient tells you whether you’re looking at a new introduction or a mature infestation that’s already spread.
Start at the head of the bed. Work outward. Don’t touch anything until you’ve looked at everything.
What it looks like: Ink-dot marks, 1–2mm, black or rust-brown, clustered along the piping seam near the head of the bed. On light fabric they bleed slightly at the edges, like marker on paper towel.
What it rules in: Active feeding within arm’s reach. This is digested blood, and it’s the single most reliable indicator there is.
What it rules out: Nothing else makes this exact mark. Mold spots don’t bleed. Dirt doesn’t cluster on a seam. If you’re unsure what you’re looking at, what bed bug poop looks like breaks down the difference in detail.
What it looks like: Streaks rather than dots — a few millimeters long, usually near the shoulder or hip area of the sheet.
What it rules in: Recent feeding, within the last night or two. Smears mean a fed bug got rolled on.
What it rules out: Fleas and mites. Neither leaves smears at this size and location.
What it looks like: Translucent, amber, hollow — the shape of the bug but empty and slightly brittle. They collect in the gap between headboard and wall, and along the underside of the top rail.
What it rules in: A breeding population. Bugs shed five times as they mature, so skins mean reproduction, not a single hitchhiker.
What it rules out: A one-off introduction from a hotel or bus seat.
What it looks like: Apple-seed sized, flat if unfed, swollen and darker if fed. The corners of the box spring, where the gauze fabric wrinkles, are the highest-yield spot in most homes.
What it rules in: Established, current activity.
What it rules out: A historical infestation that was already treated.
What it looks like: Pearl-white, about a millimeter, slightly curved, cemented in place. They sit in the wood joints and screw holes of nightstands and bed frames — never loose on flat surfaces.
What it rules in: An infestation that’s at least a few weeks old and actively expanding.
What it rules out: Recent arrival.
What it looks like: Raised welts in a line or loose cluster of three or four, on skin exposed during sleep — arms, shoulders, neck, ankles.
What it rules in: Very little on its own. Bite reactions vary enormously; some people show nothing at all.
What it rules out: Also very little. This sign is supporting evidence only. Never treat based on bites alone.
What it looks like: Nothing — you smell it. Often described as overripe raspberries or damp coriander.
What it rules in: A heavy, mature population. Odor is a late-stage sign.
What it rules out: A light infestation, which is usually odorless.
Quick reference table
| # | Sign | What it rules IN | What it rules OUT |
| 1 | Dark seam spots | Active feeding nearby | Fleas, mold, general grime |
| 2 | Sheet smears | Feeding in last 1–2 nights | Fleas, dust mites |
| 3 | Shed skins | Breeding population | Single hitchhiker |
| 4 | Live bugs in box spring | Current, established activity | Old/treated infestation |
| 5 | Eggs in joints | Weeks-old, expanding | Recent introduction |
| 6 | Bite patterns | Supporting evidence only | Nothing conclusive |
| 7 | Musty odor | Heavy, mature population | Light infestation |
Older Detroit housing stock — the pre-war flats in Southwest, the brick four-squares in Boston-Edison, the century-old duplexes across the east side — has hiding places that newer construction simply doesn’t.
Radiator gaps. Cast iron radiators sit on brackets with a half-inch gap behind them, and the paint has usually been built up over decades into a ridged, flaking surface. That’s ideal harborage: dark, undisturbed, and warm during heating season. Look at the wall directly behind the radiator nearest the bed, and at the pipe collar where it enters the floor.
Original wood trim. Baseboards and window casings in these homes are often solid wood with deep profiles, and after a hundred years the joints have opened up. The gap where baseboard meets floor, especially along the headboard wall, holds staining and skins that never get cleaned out.
Plaster cracks behind headboards. Lath-and-plaster walls crack. Behind a headboard, those cracks go unnoticed for years, and they’re a direct route into the wall cavity. If you see spotting concentrated around a crack rather than spread along the wall, that’s a harborage point, not a travel path.
Shared walls in converted flats. Where a single-family home was split into upper and lower units, the original chases — old gas lines, removed pipe runs — connect the units. Activity in a neighboring unit reaches yours through those routes. Where bed bugs hide covers the full harborage map.
If you found signs 1 through 5 — physical evidence, not just bites — you have an infestation. Don’t start moving furniture, don’t bag everything, and don’t set off a fogger. Foggers scatter a contained population into wall voids and turn a one-room problem into a whole-unit problem.
If you found only bites, or only the odor, hold off. Bites alone are too unreliable to act on, and odor without visual evidence usually means the source is a neighboring unit.
Either way, leave the room as it is. A technician needs to read the same evidence trail you just read, and an intact room cuts inspection time dramatically. If you’re ready to move forward, here’s how to prepare your home — and it’s less than you’d think. When you’re ready to confirm what you’re looking at, a professional bed bug inspection in Detroit will map the full extent of the population, including the harborage points behind radiators and inside wall cavities that a flashlight check can’t reach.
Usually dark spotting along the top seam of the mattress near the head of the bed. It shows up before bites do in most cases, because bite reactions can take days to appear — or never appear at all.
Yes. Bugs feed for a few minutes at night and spend the rest of the time in cracks and seams. In a light infestation you’ll find the evidence — spotting, skins, eggs — long before you see a live bug.
Bed bug spotting bleeds slightly into fabric, like ink on a napkin, and clusters along seams and edges rather than spreading randomly. Dirt sits on the surface and wipes off dry. Digested blood smears reddish-brown when wiped with a damp cloth.
Beyond the bed, the high-value spots are radiator gaps, the joint where original wood baseboard meets the floor, plaster cracks behind headboards, and old utility chases in converted flats.
Yes. In multi-unit buildings they travel through wall voids, shared plumbing chases, and outlet boxes. Odor or light activity with no clear source in your own unit often points to a neighboring one.