Adult fleas are brown, wingless, laterally compressed insects from 1 to 2.5 mm long. Flea larvae vary in length from 4 to 6 mm when mature and are slender, white, cylindrical and legless with 10 to 12 moderately long setae on each body segment. The pale brown head has no eyes. The pupa is shaped somewhat like the adult and develops in a white, oval, silken cocoon about 4 mm long which is often covered with sand, lint, or dust. They are commonly found in clothing, bedding or near areas where host animals sleep or in the fur of the host animal.
Fleas spread through homes, buildings and yards.
Each species of flea, however, usually feeds on a limited number of specific animals. Human fleas occasionally feed on swine and dogs. The oriental rat flea feeds primarily on commensal rodents but sometimes feeds on man. Scratching the area of the bite causes the skin to be irritated. Some fleas, especially the oriental rat fleas, are capable of transmitting diseases such as endemic typhus and bubonic plague.