Insects that feed on Humans. -- the Blood Suckers! Bedbugs, Fleas, Mites, Mosquitoes, Lice, Ticks. Get an overview here.
Bed Bugs Biology and Habits
Both adult and nymph suck blood; humans are the preferred host

Hides during the day, usually near sleeping areas in cracks in walls, behind baseboards, under mattresses, in box springs, in furniture, under wallpaper or pictures, in drapes, under rugs, under window or door frames.

At one time, bed bugs were primarily found most often in barracks, camps, jails, rooming houses, homeless shelters, old hotels, other shared sleeping quarters.

Today, found in hotels, apartments, schools, private homes, and other sites.
Also can infest hospitals, nursing homes, trains, planes, buses, cruise ships, theaters, moving vans, etc.

Leaves dark fecal spots on mattresses, bed clothes, clothing, and even walls, ceiling, and other surfaces.

Scet glands emit a "sickly sweet" odor

Feeds mainly at night, hides during day

Bed bugs travel up to twenty feet to feed, and occasionally much further.

Can go for months between feedings

Often transported to new locations in luggage, used beds or bedding, secondhand furniture, or clothing

Can migrate from one room or apartment unit to the next through pipe and wiring runs, and in wall and ceiling voids, much as cockroaches move
Painless bite can leave an itchy welt
Feeding does not spread any diseases.