Bed bugs are hard to identify because they are similar in appearance to many other smaller insects. They are especially similar looking to their close relative, the bat bug. If you have collected a bug you suspect is a bed bug, keep it for your PCO (Pest Control Operator) for verification. Alternatively, you may post a picture of the bug (use a macro setting on your camera – the flower icon – for good quality close shots) on our forums for identification.

In the picture below, some bed bugs are longer than others because they have recently fed on blood. The feeding engorges their entire bodies, leaving them looking like almost an entirely different insect. Also note the difference in appearance between the fed and unfed bed bug nymphs – the transparent coloring allows us to see the richer red of the blood. It is never easy to quickly identify a bed bug, as they vary in appearance depending on when you observed them in their life cycle. Hopefully the picture above can guide you along in identification.

Bed bugs come in many different sizes, as they have 5 different stages in their life cycle, requiring a molt each time they evolve.

Bed bug adults are close in size to the seeds of a jalapeño pepper (nearly exact). I have also heard some individuals compare bed bugs to the size of an apple seed, although I would venture to say that is a bit bigger than a bed bug.

Also see this related post, showing bed bugs measured against a 1 centimeter measurement.

How big are bed bugs?

The blood-sucking parasites – bed bugs are found all over the world.  They have an uncanny efficiency to travel from one place to another through various surprising means of transport such as – luggage, airplanes, trains and clothes, etc. The bed bugs and its bites are a growing concern to humanity.  Therefore, it is quite important to know the life cycle of bed bugs. This aids in ascertaining an infestation, if any, and move on to consider the type of treatment.

The Life Cycle of the Bed Bugs:


The life process of a bed bug essentially goes through five stages. The adult female bed bug lay eggs that are less than 1.0 mm long. These eggs are milky white, tiny and oval shaped like a poppy seed.  The eggs are usually sticky, which makes it quite difficult to remove them during the treatment process. The female lays up to five eggs per day and has the capacity of laying about 400 to 500 during her lifetime.  The hatching process of the eggs takes up to 14 days. The hatchlings look like tiny dust specs and are known as nymphs. The nymphs are born by pushing out the egg-cap.

The Nymphs

Every stage of growth is called an instar. Since a bed bug goes through five stages before it grows into an adult, each stage is termed as first instar, second instar and so on. The size of the first instar nymph is about 1.5 mm long, about the size of a pinhead. It remains almost invisible because of its clear color due to lack of nutrition. The young nymphs need a blood feed before they can progress to the next stage of development. They also get color after each blood meal.  In each stage, the bedbug grows larger than its current exoskeleton structure. The young nymph thus needs to molt or shed its skin at each stage of development.

The second instar nymphs are about 2mms in length and will need a blood feed to develop further. It is now easier to see the internal organs of the nymphs. They again molt their skin to enter the next stage of evolution.  Each stage takes up to a period of seven days to complete, under healthy conditions. The bed bugs need enough nutrition to complete the shedding of the skin. The color and size of the nymph vary in each stage.

Third instar nymph – 2.5 mm, crimson red

Fourth instar nymph – 3 mm, mahogany

Fifth instar nymph –  4.5 mm, reddish brown

The process of a blood meal, growth and molting repeats for each instar cycle until the bedbug becomes a fifth instar nymph.  Once the bed bug reaches the fifth, the final stage, it sheds its skin to become a fully-grown bed bug.  The grown bed bugs are flat in shape before the blood meal. A fed adult bug takes the shape of the torpedo. The bed bugs in this stage need regular blood feed to get sufficient energy to produce eggs or sperms.