How can I distinguish a female bed bug from a male bed bug? - briefly
Female bed bugs are noticeably larger, with a broader, more rounded abdomen and a visible ovipositor near the rear, while males are smaller, have a narrower abdomen, and possess a retractable genital capsule.
How can I distinguish a female bed bug from a male bed bug? - in detail
Female and male bed bugs can be separated by several anatomical traits that become apparent under magnification (10‑40×). The most reliable indicators are:
- Body size – females are consistently larger, typically 5.0‑5.5 mm long, while males range from 4.5‑5.0 mm.
- Abdominal shape – a gravid female shows a rounded, bulging abdomen that expands as eggs develop. Males possess a more tapered, cylindrical abdomen.
- Sternite curvature – on the ventral side of the ninth abdominal segment, males display a distinct, hooked (or “C‑shaped”) structure used for copulation; females lack this curvature.
- Ovipositor presence – the terminal segment of a female’s abdomen ends in a short, blunt tip adapted for egg laying; males have a pointed, elongated tip without ovipositor features.
- Genital plate visibility – in males, the paramere (external genitalia) can be seen as a pair of small, dark sclerotized plates on the underside of the abdomen; females do not exhibit these plates.
- Egg load – a mature female often carries 1‑5 eggs visible through the translucent cuticle, especially after a blood meal; males never contain eggs.
Behavioral cues can support visual identification but are less definitive:
- Females lay eggs in concealed cracks after feeding; males do not engage in oviposition.
- Mating rituals involve the male mounting the female’s dorsum; observing a pair in this position confirms the sexes.
For accurate determination, collect specimens, place them on a white background, and examine the ventral abdomen with a stereomicroscope. Record measurements and note the presence or absence of the male‑specific genital hook and the female’s egg‑bearing abdomen. Combining size, abdominal morphology, and genital structures yields a conclusive sex identification.