What Do Bed Bugs Look Like? Every Life Stage, Actual Size

An adult bed bug is 4 to 5 mm long, flat as a business card, and reddish-brown — about the size and colour of an apple seed. That single comparison resolves most identifications on the spot. Everything else on this page exists for the harder cases: the 1 mm nymph you can barely see, the swollen deep-red adult that has just fed and looks nothing like the photographs, and the four other insects that turn up in Washington homes and get blamed on bed bugs every week.

Getting this right before you call anyone matters more than it sounds. Bed bug treatment in Washington runs $270 to $900 per room depending on method, and a misidentification means either paying for the wrong treatment or waiting three weeks while an actual infestation doubles.

What an adult bed bug looks like

An adult bed bug looks like a flattened brown oval, roughly 4 to 5 mm long and 3 mm across, with six legs and a pair of short antennae. The flatness is the defining feature and the reason they are so hard to find — an unfed adult is thin enough to slide into a gap you could not fit a credit card into.

Work through these five features in order. If all five match, you have a bed bug.

• Shape. A broad, symmetrical oval. Not tapered, not elongated, not domed like a beetle.
• Profile. Flat from above when unfed. This is the feature that survives all the others.
• Colour. Reddish-brown, mahogany, similar to a coffee bean. Never metallic, never patterned.
• Antennae. Short — about a quarter of body length. Long antennae mean cockroach.
• Wings. None. Small non-functional wing pads sit behind the head, but there is no wing case covering the abdomen the way a beetle has.

The abdomen carries visible horizontal segments, which look like fine banding across the back half of the body. Under a phone camera at maximum zoom, that banding is usually the detail that settles a doubtful identification.

Every life stage at actual size

Bed bugs pass through six stages after hatching: five nymph stages and then adulthood. Each nymph stage requires a blood meal before the insect can moult into the next, which is why an established infestation contains insects of every size at once.

Finding a range of sizes in one place is itself a diagnostic finding. A single adult could have arrived in a suitcase yesterday. Adults, mid-size nymphs and eggs together means the population is breeding where you found them.

Stage	Length	Colour	Where you find it
Egg	~1 mm	Pearl white, slightly sticky	Cemented into seams and cracks, in clusters
1st instar	~1.5 mm	Translucent, almost colourless	Deepest in harbourage, easily missed
2nd–3rd instar	2–2.5 mm	Straw to pale tan	Seams, headboard joints
4th–5th instar	3–4.5 mm	Tan to light brown	Same harbourage as adults
Adult	4–5 mm	Reddish-brown	Mattress seams, bed frame, wall voids

How feeding changes what you are looking at

Feeding changes a bed bug’s appearance so much that the same insect photographed before and after looks like two species. This is the single biggest reason people compare what they found against an image online and conclude it is something else.

An unfed adult is flat and reddish-brown. Within minutes of a blood meal it swells, elongates, and darkens to a deep purplish-red — the body wall stretches, the segment banding stands out sharply, and the profile changes from flat to rounded. Nymphs show this even more dramatically: a translucent first-stage nymph turns into a visibly bright red speck, because the blood meal is simply visible through a body wall that is nearly transparent.

If you crush one and it leaves a red smear, that is a fed insect. That test tells you it has eaten, not what species it is, and it destroys the specimen you would otherwise want to keep.

Keep the specimen

Anything you find should go into a clear zip bag or a small jar with a lid, not down the toilet. A physical specimen is worth more than any photograph when a technician arrives, and it settles the question in seconds rather than turning the first ten minutes of a paid visit into a debate. Sticky tape works if nothing else is to hand — press it over the insect and fold the tape onto itself.

What bed bug eggs and shed skins look like

Eggs and shed skins are more commonly found than live insects, because they stay put while the insects move. Both are pale, roughly 1 mm, and easy to mistake for lint or dust until you know the difference.

Eggs are pearl white, slightly translucent, and shaped like a grain of rice with a rounded end. They are cemented in place with a glue the female produces, so they do not roll or brush away easily — a dry brush will move lint but leave eggs behind. Shed skins, or exuviae, are the empty amber-coloured husks left after each moult. They keep the full shape of the insect, including legs and antennae, but they are hollow and translucent, like a bed bug made of cellophane.

Shed skins are strong evidence because they cannot arrive on their own. An insect can hitchhike in on a bag, but a shed skin means one lived, fed and grew where you found it. The full guide to eggs, shells and casings covers how to tell a viable egg from a hatched one, which changes how urgent the situation is.

What people usually find instead

Most specimens brought to a technician in Washington are not bed bugs. Four look-alikes account for the large majority.

• Carpet beetle larvae. Fuzzy, bristled, and distinctly hairy under a phone camera. Bed bugs are smooth and hairless. Adult carpet beetles are round, mottled, and fly.
• German cockroach nymphs. Longer, tapered, fast-moving, with antennae as long as the body and two pale stripes down the back.
• Spider beetles. Rounder and more domed, with visibly long spidery legs and a body that looks like a small shiny seed on stilts.
• Bat bugs. Genuinely close relatives that need a microscope to separate — the hairs on the pronotum are longer than the eye is wide. Rare, but they do occur in older Washington buildings with roof or attic bat roosts.

That last one matters more here than in most states, because it changes the treatment entirely. Treating bat bugs as bed bugs fails every time, since the actual host is still in the attic. The look-alike guide goes through all four in detail.

Found one. What now?

Finding a single bed bug is not proof of an infestation, and it is not nothing either. The next step is confirming whether it is breeding rather than passing through, which means looking for the evidence they leave rather than for more insects.

First, bag the specimen. Second, check the mattress seams, the box spring underside and the headboard joints with a torch held at a low angle — those three locations account for most first finds. Third, look for dark staining along seams, which is digested blood and the most reliable single indicator there is. Finally, resist the urge to move anything out of the room, because moving infested furniture is the most common way a one-room problem becomes a whole-home one.

If two or more of those checks come back positive, it is worth booking an inspection. Call us and we will get someone out, and the call costs nothing whether you book a treatment or not. Our inspection guide covers what a visual survey should include and where canine detection is genuinely worth the $300 to $600 it adds.