Bed bugs are wingless insects, roughly oval in shape, 4-5mm long when fully grown, and are fast runners. They are rust brown in colour and change to a deeper red brown following a blood meal. Bed bugs are dorsoventrally flattened and being thin means that they can hide in narrow cracks and crevices, making detection often very difficult.

The two main species that bite humans include the common bed bug, Cimex lectularius, and the tropical bed bug, Cimex hemipterus. The presence of the former species has been long known in Australia, whereas the tropical bed bug was only recently recognised in the country by the Medical Entomology Department, ICPMR.

There are five juvenile stages known as nymphs, which are miniature versions of the adults in appearance. Each nymphal stage requires at least one blood meal to moult to the next stage and it takes 5-10 minutes for complete engorgement to occur. The entire nymphal development takes 6-8 weeks, while the adult bed bugs can live on average for 6-12 months. All nymphal stages and adults of both sexes require blood for nutrition and development. After mating, each female lays 2-3 eggs a day throughout her lifespan. The cream coloured eggs (1mm in length) are cemented on rough surfaces of hiding places, and will hatch within around 10 days at room temperature, but longer in cooler conditions.

The mouthparts of bed bugs are especially adapted for piercing skin and sucking blood. Like most blood sucking arthropods, they inject saliva during feeding, which has anticoagulant properties. Bed bugs respond to the warmth and carbon dioxide of a host and quickly locate a suitable feeding site. They tend not to live on humans and the only contact is for a blood meal. Most blood feeding occurs at night, and they generally seek shelter during the day and become inactive while digesting the blood meal. However, bed bugs are opportunistic and will bite in the day especially if starved for some time. They can survive for long periods without feeding. While their preferred host is human, they will feed on wide variety of other warm-blooded animals including rodents, rabbits, bats, and even birds.

Being a cryptic species, bed bugs shelter in a variety of dark locations, mostly close to where people sleep. These include under mattresses, floorboards, paintings and carpets, behind skirting, in various cracks and crevices of walls, within bed frames and other furniture, and behind loose wallpaper. Bed bugs tend to stay in close contact with each other and heavy infestations are accompanied by a distinctive sweet sickly smell. Blood spotting on mattresses and nearby furnishings is often a tell tale sign of an infestation.

Bed bugs are one of the great travellers of the world and are readily transported via luggage, clothing, bedding and furniture. As such, they have a worldwide distribution.