The bed bug (_Cimex lectularius_) is an obligate blood-sucking insect; adults are about 4–5 mm long, reddish-brown, with a flat, oval body — this flattened body shape enables them to squeeze into extremely narrow crevices.

Bed bugs have no wings, cannot fly or jump, and move solely by crawling.

They are nocturnal insects, hiding during the day in mattress seams, headboard joints, baseboard cracks, and other concealed locations, emerging at night to seek a human host in deep sleep for a blood meal.

Each blood meal lasts 3–10 minutes.

Bed bug development undergoes incomplete metamorphosis: egg → nymph (5 instars, requiring one blood meal before each molt) → adult.

Under favorable conditions, development from egg to adult takes about 5 weeks.

The origin of bed bugs can be traced back to parasitic insects on bats, likely transferring to humans when humans began inhabiting caves.

Bed bugs were nearly eradicated in developed countries in the mid-20th century due to widespread DDT use, but experienced a global resurgence in the early 21st century due to increased international travel, the ban on DDT, and insecticide resistance.