Bed bugs have tormented humans for millennia, so detested that their mere mention can make hearts race and arms itch. There are approximately 100 species of bed bugs, but thankfully only three of them feed on humans. So, why are these unwelcome houseguests so difficult to defeat? And is there any way to get rid of them for good? Gale E. Ridge investigates the tremendous staying power of bed bugs. Lesson by Gale E. Ridge, directed by Devin Clark, Augenblick Studios.