What do bedbugs look like and what size are they? - briefly
Bedbugs are flat, oval, wingless insects with a reddish‑brown hue and a smooth, non‑shiny exoskeleton. Adults measure approximately 4–5 mm long, comparable to the size of an apple seed.
What do bedbugs look like and what size are they? - in detail
Bed bugs are small, wing‑less insects belonging to the family Cimicidae. Their bodies are soft, dorsoventrally flattened, and roughly oval, allowing them to hide in tight crevices. The exoskeleton is covered with a fine, translucent cuticle that appears brown when unfed and turns a reddish‑brown after a blood meal due to the ingested hemoglobin. The head is concealed beneath the thorax, and the antennae consist of five segments that are lightly visible at the front. Each side of the thorax bears two elongated, curved fore‑wings (hemelytra) that are reduced to protective pads rather than flight structures. Legs are slender, ending in small claws adapted for clinging to fabrics and surfaces.
Size varies throughout development:
- First‑instar nymphs: 1.5–2.0 mm (0.06–0.08 in) in length, translucent and pale.
- Second‑instar nymphs: 2.0–2.5 mm (0.08–0.10 in).
- Third‑instar nymphs: 2.5–3.0 mm (0.10–0.12 in).
- Fourth‑instar nymphs: 3.0–3.5 mm (0.12–0.14 in).
- Fifth‑instar nymphs: 3.5–4.5 mm (0.14–0.18 in).
- Adult males and females: 4.5–5.5 mm (0.18–0.22 in) when unfed; length can increase to about 6 mm (0.24 in) after feeding, while width remains around 2.5 mm (0.10 in).
The abdomen expands noticeably after a blood meal, giving the insect a more rounded appearance. Color deepens from light tan to a richer, rusty hue as digestion progresses. These morphological traits—flat, oval shape, concealed head, reduced fore‑wings, and progressive size increase from nymph to adult—enable identification of bed bugs in various stages of their life cycle.