Female cat fleas remain on the host (unlike most other fleas) and lay about 20 to 30 eggs per day on the animal. Cat flea eggs are pearly white, oval, and about 1/32 inch long. The eggs are smooth, they readily fall from the pet and land on surfaces like bedding and carpeting in the animalˇs environment. They hatch in about 2 days. The whitish, wormlike larvae feed on dried blood and excrement produced by adult fleas feeding on the pet. Larval development is normally restricted to protected places where there is at least 75% relative humidity. They feed and crawl around for 5 to 15 days at 70 to 90F before they build small silken cocoons in which they develop into adult fleas (pupate). The pupae are usually covered with local debris for visual camouflage. At room temperatures, the entire life cycle may be completed in about 18 days. An adult cat flea generally lives about 30 to 40 days on the host; it is the only stage that feeds on blood. Fleas may be found on pets throughout the year, but numbers tend to increase dramatically during spring and early summer.
The cat flea is suspected of transmitting murine typhus to humans, but its primary importance is in its annoyance to people and pets. Cat fleas readily try to feed on almost any warm-blooded animal. Some people are bothered by the sensation of fleas walking on their skin, but bites are the major nuisance. Bites tend to be concentrated on the lower legs but can also occur on other parts of the body.
The bite consists of a small, central red spot surrounded by a red halo, usually without excessive swelling. Flea bites usually cause minor itching but may become increasingly irritating to people with sensitive or reactive skin. Some people and pets suffer from flea bite allergic dermatitis, characterized by intense itching, hair loss, reddening of the skin, and secondary infection. Just one bite may initiate an allergic reaction, and itching may persist up to 5 days after the bite. Cat fleas may also serve as intermediary hosts of dog tapeworms. Cats or dogs may acquire this intestinal parasite while grooming themselves by ingesting adult fleas that contain a cyst of the tapeworm.