How to determine if a bedbug is female or male? - briefly
Inspect the insect under magnification: females display a larger, rounded abdomen with a visible ovipositor, whereas males have a slimmer abdomen and no ovipositor.
How to determine if a bedbug is female or male? - in detail
Bed bugs can be sexed only after they reach the adult stage; earlier instars lack distinguishable reproductive structures. Accurate identification requires a stereomicroscope or a magnifying lens of at least 40×.
Key morphological differences
- Size: Adult females typically measure 5.5–6.5 mm, while males are 5–5.5 mm. The size gap is small and should be considered alongside other traits.
- Abdominal shape: Females have a broader, more rounded abdomen to accommodate eggs; males display a narrower, slightly tapered abdomen.
- Terminal segment: In females, the ninth abdominal segment ends in a short, blunt ovipositor. Males possess a pointed terminal segment with a visible paramere (copulatory organ) on the ventral side.
- Spermatheca: A translucent sac located near the dorsal midline of the abdomen is present only in females; it stores sperm after mating and can be seen as a small, darkened area under magnification.
- Genitalia visibility: Male genital structures often appear as a pair of small, curved hooks on the ventral side of the terminal segment; females lack these hooks.
Procedure for sex determination
- Collect a live specimen using a fine brush or forceps; place it in a shallow, ventilated container.
- Immobilize the bug by chilling it on ice for 5–10 minutes; this reduces movement without causing damage.
- Position the specimen dorsal side up on a clean slide; cover with a coverslip if needed for stability.
- Examine under the microscope, focusing on the posterior abdomen. Adjust illumination to enhance contrast.
- Identify the relevant structures listed above; compare size and shape to the described criteria.
- Record the observation (female or male) and, if needed, photograph the diagnostic features for documentation.
Additional considerations
- Mating status: Mated females may exhibit a fuller abdomen due to developing eggs; unmated females can appear similar to males in size, reinforcing the need to check genital morphology.
- Specimen condition: Damage to the terminal segments can obscure key features; avoid handling that tears the abdomen.
- Species verification: Ensure the insect is Cimex lectularius or a related bed‑bug species, as sexual dimorphism can vary slightly among taxa.
By following these steps and focusing on abdominal morphology, the sex of an adult bed bug can be reliably determined.