Fleas are obligate ectoparasites of mammals and birds. Both males and females use piercing-sucking mouthparts to feed on the blood of their host.  Most species are associated with rodents.  Adults are small, wingless, laterally flattened insects.  They have long legs adapted for jumping, and their bodies are often covered with large spines known as ‘combs’ or ctenidia.  The legless larvae usually live in the host's nests where they feed on organic matter, including feces and dried blood shed by feeding adults. Some species are vectors of human disease including plague (Yersinia pestis) and murine typhus (Rickettsia typhi).