Discerning the difference between female and male bed bugs can give you an indication of how serious a bed bug infestation is and how quickly the colony will grow under the right temperature and feeding resource conditions. While male and female bed bugs look very similar, there are key differences between the two, including size, behaviour and symmetry that will help you discover the truth.
Observe live bedbugs reproducing if you can, as this is the easiest and surest way to differentiate male from female bed bugs. Usually the male will rest on top of the swollen abdomen of the female (female bed bugs must have a blood meal before insemination.)
Compare bedbugs against one another to see the differences between male and female. Females tend to have more symmetrical bodies and more rounded rear ends, while the males can be smaller with sharper, sometimes asymmetrical end points.
Look at the bedbug's first set of legs, located on the head or neck below the antennae. Females tend to have their first legs protrude higher up on their bodies, appearing to emerge from the upper neck and even head of the animal, while males (partially due to their smaller size) have their first set of legs lower down on the neck or even main body.