What do male and female bed bugs look like, and what are their sizes? - briefly
Both sexes are reddish‑brown, oval, and wingless; females are larger, typically 5–7 mm long, while males measure about 4–5 mm. After a blood meal, each expands, nearly doubling its length.
What do male and female bed bugs look like, and what are their sizes? - in detail
Adult bed bugs are wingless, oval insects measuring roughly 4.5–5.5 mm in length when unfed and expanding to 6–7 mm after a blood meal. Their bodies are flat on the dorsal side and become balloon‑like when engorged. The exoskeleton exhibits a reddish‑brown hue that darkens to a deep mahogany after feeding; immature stages appear paler.
Males are marginally smaller than females, typically 4.3–5.0 mm long unfed. The male abdomen is narrower and more tapered, ending in a visible genital capsule on the ventral surface. Females reach 5.0–5.8 mm unfed, with a broader, rounded abdomen that accommodates developing eggs. The female’s posterior segment bears a subtle ovipositor, discernible only under magnification.
Both sexes share the same external structures: a six‑segmented antenna, a short beak‑like rostrum for piercing skin, and a pronotum that covers the head. The legs are slender, each ending in a pair of claws adapted for clinging to fabric and mattress seams. No wings are present; locomotion relies on crawling.
Size variations after feeding are pronounced. An unfed male may swell to 6.5 mm, while a fed female can exceed 8 mm in length, the abdomen expanding to nearly twice its original width. Weight increases from approximately 0.5 mg (unfed) to 5 mg (fully engorged).
Key identifiers:
- Length (unfed): males ≈ 4.3–5.0 mm, females ≈ 5.0–5.8 mm.
- Length (fed): males ≈ 6.0–6.5 mm, females ≈ 7.5–8.0 mm.
- Color: reddish‑brown, darkening after a blood meal.
- Abdomen shape: male – tapered; female – rounded, egg‑bearing.
- Ventral genital structures: male – hooked paramere; female – ovipositor.
These morphological details enable reliable differentiation between the sexes in both field inspections and laboratory analysis.