Adult fleas are brownish-black in colour, and are parasitic on warm-blooded animals. The fleas most commonly found in houses are cat fleas (ctenocephalides felis) which are approximately 2-3mm in size, and are responsible for the majority of flea infestations. Dog fleas, bird fleas, and occasionally human fleas may also occur.

Female fleas lay their eggs in the nest or bedding of the infested animal or in dust and crevices in buildings. The eggs develop into bristly legless larvae which pupate and turn into adults within about 7 weeks. Flea larvae feed on debris and excreta of adult fleas in the sleeping place of the host animal. Adult fleas feed on the blood of the host.