Don't let the bedbugs bite! Actually, if you were to worry about all of the parasites living on your body (sometimes helping you out), you'd never fall asleep in the first place. As a living organism part of a bigger ecosystem, humans play host to unumerable other living things. This Topic In Depth offers a look into the fascinating world of Human Ectoparasites. The first stop -- a page from encyclopedia-style Web site InnVista -- offers a brief introduction to some of the ectoparasitic species that make their living off the human body (1). The next two sites contain science news articles courtesy of the Australian Broadcasting Corporation. The first article relates how the evolution of human body lice was made possible when we developed the habit of wearing clothes some 40,000 years ago (2). The second describes an alternative hypothesis as to why humans lost their fur. The University of Sydney and Westmead Hospital, Australia offers a quick introduction to the bedbug in the following Web site (4), while the University of Kentucky entomology department does the same for chiggers in the next (5). Kansas State University offers a few pictures and interesting tidbits on tooth amoebas, the toothbrush-fleeing microscopic parasites found where the teeth meet the gums (6). Don't worry, tooth amoebas are generally good for you. Another example of a beneficial ectoparasite is the leech, which is making a comeback in medical circles for its anticoagulant properties and other medicinal uses as related in an article from the BBC News (7). And finally, Duke University offers a intriguing introduction to eyebrow mites, benign parasites that live in our eyebrow follicles and are thus somewhat limited in their choice of mates (8).