Fleas are tiny, blood-sucking insects that are seriously annoying to cats and their owners. Their bites are itchy, and they can carry and transmit disease and other parasites. The ordinary cat flea - Ctenocephalides felis – is the most common external parasite of domestic cats. It also affects dogs. Adult fleas are dark brown to black, fairly flat and about 2 to 3 millimeters in length. They usually can be seen with the naked eye. Fleas can’t fly, because they don’t have wings. However, they have well-developed, extremely powerful hind legs that give them amazing jumping capabilities. Like rabbits, fleas reproduce rapidly. Two fleas can produce 2000 fleas in a single 4-month lifespan. Adult fleas live on the skin of a host animal. Different types of fleas gravitate toward different hosts, including cats, dogs, rabbits, rodents, horses, birds and people. However, if they are hungry enough, fleas will feed on almost anyone they can hop onto. Sometimes, fleas can be seen scurrying under the cat’s (or other host’s) fur, but they can be quite difficult to catch.