What do house bedbugs look like and what are their sizes? - briefly
They are flat, oval, reddish‑brown insects with a pointed head and no wings. Adults measure 4–5 mm in length, expanding to about 6–7 mm after feeding, while nymphs range from 1.5 mm up to the adult size.
What do house bedbugs look like and what are their sizes? - in detail
Household bedbugs are small, dorsoventrally flattened insects belonging to the family Cimicidae. Adults possess an oval body roughly 4–5 mm long, resembling a tiny apple seed. The exoskeleton is smooth, lacking hairs or wings, and the head is not distinctly separated from the thorax. Six short legs emerge from the thorax, each ending in a claw for gripping fabric. Antennae are slender, four‑segmented, and positioned near the mouthparts, which include a beak‑like proboscis used for piercing skin.
Coloration changes with feeding status. Unfed specimens appear matte, light brown to tan. After a blood meal, the abdomen expands and turns reddish‑brown, sometimes appearing almost black. The dorsal surface may show a faint, pale, crescent‑shaped mark near the middle, known as the “c‑shaped” or “h‑shaped” stigma, which becomes more visible after several molts.
Size varies across developmental stages:
- First‑instar nymph: 1.5–2 mm, translucent, without distinct markings.
- Second‑instar nymph: 2–2.5 mm, slightly more opaque.
- Third‑instar nymph: 2.5–3 mm, developing the characteristic c‑shaped stigma.
- Fourth‑instar nymph: 3–3.5 mm, fully formed stigma, still lighter than adults.
- Adult: 4–5 mm in length, 2.5–3 mm in width, body depth about 1 mm.
Adults may reach up to 6 mm after a large blood meal, while unfed individuals retain the lower end of the range. The incremental growth reflects each molt, with the exoskeleton shedding to accommodate increased size.