How to determine a bedbug's sex? - briefly
Under magnification, males are identified by a pair of curved genital arches on the ventral abdomen, whereas females lack these arches and display a larger, more rounded abdomen often showing a visible ovipositor.
How to determine a bedbug's sex? - in detail
Identifying whether a bed bug is male or female requires examination of adult specimens under magnification. Immature stages lack distinguishable sexual characters and cannot be reliably sexed.
The primary morphological markers are located on the ventral side of the abdomen. In males, the ninth abdominal segment bears a pair of elongated, curved structures called parameres, which form part of the aedeagus. These appear as slender, hook‑shaped projections when viewed from the underside. Females possess a single, rounded ovipositor on the same segment; it is shorter and broader, ending in a blunt tip. The ovipositor is often concealed by a small membranous covering that can be lifted with a fine probe.
Additional, less definitive cues include:
- Size: males are typically 1–2 mm longer than females, though overlap is common.
- Coloration: females may exhibit a slightly darker dorsal hue due to a fuller abdomen after engorgement.
- Antennae: no reliable difference; both sexes have identical antennae.
Practical procedure:
- Capture an adult specimen and place it on a clean slide.
- Anesthetize with a brief exposure to cold (refrigerator) or CO₂ to prevent movement.
- Position the bug dorsal side up, then gently turn it to expose the ventral abdomen.
- Use a stereomicroscope (≥40× magnification) to locate the ninth abdominal segment.
- Observe for the presence of parameres (male) or ovipositor (female); record the finding.
- If structures are ambiguous, dissect the terminal segment with fine forceps to reveal internal genitalia.
Molecular methods, such as PCR amplification of sex‑linked genes, exist but are rarely employed outside research settings due to cost and complexity. For most pest‑control professionals, visual inspection of adult genitalia provides a rapid and accurate determination of sex.