Fleas are small parasitic insects, in the order Siphonaptera, which feed off of the blood of their host. All fleas live on the skin of their host animal, and there are different species of fleas which feed off of cats, dogs, rabbits, rodents, and humans (although if hungry, a flea of any species will feed off of any available host). Fleas are known for their ability to jump great distances and for their fast reproduction rates.