There are several species of bed bugs, all of which are parasites of warm-blooded animals. The common bed bug, whose preferred host is humans, is encountered less often nowadays, presumably because of improvements in sanitation. Related species, such as the bat bug and bird bug, prefer to feed on bats, birds and other wild hosts, but will also feed on humans if the opportunity arises or the preferred host dies or leaves the roost.
Typical hiding places for bed bugs are in tufts, folds and seams of mattresses, cracks in the box spring and bed frame. Heavier infestations often spread to behind baseboards, window and door casings, behind pictures, electrical switch plates, and loose wallpaper, in the pleats of drapes and upholstery of furniture.
You will either see them crawling in those listed areas when changing sheets or getting into bed etc.
Or you will find small little bits on arms and legs. You may also find telltale faecal or blood spots indicating hiding spots nearby.
They can cause allergic reactions to bed bug bites. They have a distinctive stinky smell.
We use residual insecticide sprays to treat for bed bugs and have to spray the room infected along with the bed to eradicate the problem.