What are the dimensions of household bedbugs? - briefly
Adult bedbugs are approximately 4–5 mm long and 1.5–2.5 mm wide; nymphs start at about 1 mm and increase proportionally with each molt. All stages are flat, oval, and barely visible to the naked eye.
What are the dimensions of household bedbugs? - in detail
Household bedbugs (Cimex lectularius) are small, flattened insects. Adult specimens measure approximately 4.5–5.0 mm in length (0.18–0.20 in) and 1.5–2.0 mm in width (0.06–0.08 in). Their bodies are oval when viewed dorsally and become slightly broader after a blood meal, reaching up to 6 mm (0.24 in) in length.
Nymphal stages differ in size:
- First‑instar nymphs: 1.2–1.5 mm long (0.05–0.06 in).
- Second‑instar nymphs: 1.8–2.2 mm long (0.07–0.09 in).
- Third‑instar nymphs: 2.5–2.8 mm long (0.10–0.11 in).
- Fourth‑instar nymphs: 3.2–3.5 mm long (0.13–0.14 in).
- Fifth‑instar nymphs (pre‑adult): 4.0–4.5 mm long (0.16–0.18 in).
Eggs are the smallest stage, measuring 0.5–0.7 mm in length (0.02–0.03 in) and about 0.2 mm in width (0.008 in). All stages possess a flattened dorsal surface, enabling the insects to hide in narrow crevices such as mattress seams, baseboard cracks, and furniture joints.
Variability in size arises from factors including recent blood ingestion, temperature, and genetic differences among populations. Fully engorged adults can appear up to 7 mm (0.28 in) long, while unfed individuals retain the lower end of the adult range.