The name fleas refers to many species including dog fleas (Ctenocephalides canis) and cat fleas (Ctenocephalides canis). They are parasites that feed off of blood, both human and animal, by piercing the skin from the outside and sucking blood. Fleas are wingless, dark colored bugs that range in size from 1/16 to 1/8 inch. Because they do not have wings, fleas travel from hosts by hopping. They can hop up to 7 inches in the air.