Bed Bug (Cimex lectularius) — identification, habitat & look-alikes

The common bed bug is a small, flat, reddish-brown insect that hides in cracks near where people sleep and comes out at night to feed on human blood. Bed bugs have made a strong comeback in recent decades, turning up in homes, hotels, hospitals, trains, and airplanes, usually after hitching a ride in luggage. Their bites can be very itchy, but bed bugs have not been shown to spread disease to people.

Appearance

Appearance: Adults are about the size of an apple seed, roughly 3/16–1/4 in (5–7 mm) long. Unfed, they are brown, flat, and oval; after a meal they swell up like a small balloon and look redder and longer. They have short golden hairs and only tiny wing pads, so they can't fly.

Look-alikes

Eastern bat bugCimex adjunctus

Under magnification, compare the hairs along the sides of the plate just behind the head with the width of the eye: a bed bug's hairs are shorter than the eye is wide, while a bat bug's are longer. Bat bugs normally live with bats, so finding them can point to bats in an attic or wall; an expert ID is a good idea before treatment.

Why they get mixed upThey are close relatives in the same genus, look almost identical, and can wander into living spaces.

Cockroach nymphsBlattodea

Young cockroaches have longer legs, small projections at the tail end, and run much faster.

Why they get mixed upBoth are small, brown, and come out of household cracks.

Where it lives

Typical habitats: Beds and mattresses
Furniture cracks
Hotels and shelters
Range: Found almost everywhere people live, including across the United States.
Preferred conditions: Bed bugs spend most of their time packed together in hiding spots such as mattress seams, bed frames, and wall cracks rather than on people. They can't fly and spread mostly by stowing away in luggage and furniture.

Behavior

Diet: Blood, mostly from people. A meal takes several minutes.
Activity: Mostly active at night. They find sleeping people by following warmth and the carbon dioxide in our breath. Glands on the underside give off a musty-sweet odor.

Life cycle

Clutch size: A well-fed female lays about 2–3 eggs a day, adding up to hundreds over her life. The pearly-white eggs are pinhead-sized, about 1/25 in (1 mm).
Incubation: About 10 days at room temperature. Eggs don't survive below about 57°F (14°C).
Larva: Young bed bugs () go through five stages, and each one needs a blood meal before molting. Newly hatched nymphs are whitish-yellow and nearly see-through, and they must feed within 2–3 days or die.
Lifespan: Adults can go up to six months between meals.

Cautions

Cautions: Reactions to bites range from no marks at all to itchy welts and even blisters, and some people develop allergies or lose sleep from worry. Bed bugs can carry some germs, but studies have not shown that they pass them to people.

Conservation

IUCN Red List: NENot EvaluatedNot yet assessed

Culture and stories

Culture and stories: Some bed bug populations have become resistant to common insecticides, which helps explain why infestations are hard to wipe out.