Which is larger, a bedbug or a flea? - briefly
A flea exceeds a bedbug in size; adult fleas typically measure 2–4 mm, while bedbugs are about 4–5 mm long but considerably slimmer. Consequently, the flea appears larger overall.
Which is larger, a bedbug or a flea? - in detail
Bed bugs (Cimex lectularius) measure about 4–5 mm in length when fully grown, with a flattened oval body that expands to roughly 6 mm after feeding. Their width ranges from 2 to 3 mm. Adult fleas (Ctenocephalides felis or C. canis) are typically 2.5–3.5 mm long, but their bodies are laterally compressed, giving a width of 1.5–2 mm. Both species exhibit size variation across developmental stages:
- Eggs: bed‑bug eggs ~0.5 mm; flea eggs ~0.5 mm.
- Nymphs/larvae: bed‑bug nymphs progress through five instars, reaching 2–3 mm before the final molt; flea larvae grow to 2–3 mm before pupation.
- Adults: average dimensions as noted above; some flea species (e.g., the rat flea) can exceed 4 mm, still remaining shorter than a fed bed bug.
The larger dimension of a bed bug is its length, especially after a blood meal, whereas a flea’s body is more compact. Consequently, in a direct comparison of adult specimens, the bed bug is generally longer and overall larger than the flea.