Fleas are not newcomers to this planet. Fossilized fleas have been found from as far back as the Cretaceous period. Today, fleas occupy every continent and every major island on earth. As of 1979, there was a total of 2,259 species of fleas described and named in the world. A total of 325 species can be found in the United States and Canada. Of these species at least 22 will bite man.