Adult bed bugs are small, reddish-brown insects roughly the size of an apple seed. An infestation can accelerate rapidly, so identifying a gravid, or egg-carrying, female is crucial. Identifying a gravid female requires careful observation of her size and body shape, which signals that the population is actively growing.
Visual Characteristics of a Gravid Female
A gravid female bed bug is generally the largest form of the insect encountered. An unfed adult is typically flat and oval-shaped, measuring about 5 to 7 millimeters long. The female carrying developing eggs exhibits a noticeably altered morphology, especially in her abdomen. Her abdomen becomes significantly distended, taking on a swollen, elongated, almost balloon-like appearance to accommodate the egg mass.
While the overall color remains reddish-brown, the abdominal cuticle is stretched, making the internal contents more prominent. The end of the female’s abdomen is characteristically rounded and blunt, contrasting with the more tapered or pointed abdomen of a male bed bug. A fully gravid female will look substantially larger and plumper than her male counterpart.
Distinguishing Fed from Gravid
Distinguishing a truly gravid female from an adult that has recently taken a blood meal is a common challenge. Both males and females become engorged and more reddish immediately after feeding, temporarily sharing a swollen look due to ingested blood.
The key difference lies in the shape of the posterior end of the body. Even when fully engorged, the male retains a V-shaped, more pointed tip to his abdomen. The female maintains her signature rounded, blunter abdominal end, which is exaggerated when she is gravid.
The swollen appearance of a recently fed bug diminishes within a couple of days as the blood meal is digested. A gravid female, however, maintains a consistently distended abdomen because the mass of developing eggs occupies space. This sustained plumpness is the most reliable visual indicator of active reproduction.
Reproductive Cycle and Egg Laying
A single female bed bug can lay between one and ten eggs per day after securing a blood meal. Over her lifespan, which can last several months, she may produce a total of 200 to 500 eggs.
The female selects sheltered areas close to the host to deposit her eggs. These tiny, pearl-white eggs measure about one millimeter long and are often cemented into tight cracks, crevices, mattress seams, or behind headboards. The sticky secretion used to attach the eggs makes them difficult to dislodge.
The eggs are grain-like in shape and may display a visible eye spot if they are more than five days old. Depending on temperature and humidity, these eggs typically hatch into first-stage nymphs within six to ten days. This short incubation period allows a single gravid female to quickly establish a growing population.