Adult FleaIf you have pets, or know people who do, you know about fleas. They are probably the third most hated pest behind roaches and ants. There are some 2000 species of fleas in the world but only about 10 are bothersome to humans. The most common is the Cat Flea which infests both cats and dogs. This is the same pest that was responsible for the Black Plagues of the middle ages. Fleas are also the cause of numerous allergies, and can carry the dog tape-worm that can infect humans as well as pets.