There are more than 2,200 species of fleas, but only few species are found frequently on dogs and cats; the “cat flea” (Ctenocephalides felis), the “dog flea” (Ctenocephalides canis), and two species of human fleas, (Pulex irritans and Pulex simulans). The most common flea on both dogs and cats is the “cat flea”.
Fleas have a 4-stage life cycle: egg, larva, pupae and adult. Under most household conditions, cat fleas complete their life cycle in 3-4 weeks. Depending on temperature and humidity, the range could be from as little as 2 weeks to as much as 6 months.
Flea eggs are pearly white ovals with rounded ends. Although fleas lay their eggs in the hair coat of the host, the eggs are not sticky and they readily fall off the host into the environment. A female flea will lay eggs after she has a blood meal and has mated. Under favorable conditions, a female can lay from 20-50 eggs a day and more than 2,000 over a lifetime. Eggs usually hatch in 1-6 days, depending on temperature and humidity.
Newly hatched cat flea larvae are slender, white, segmented creatures sparsely covered with short hairs. The larvae feed on organic debris in the environment, including the feces of the adult fleas, which containing the dried and partially digested host blood. Flea larvae avoid light and tend to move downward in response to gravity. As a result, they are found deep in carpet fibers or under organic debris, such as branches or leaves. They accumulate in area where the animal spends the most time, such as resting areas.
Mature larvae change into pupae inside a whitish, loosely spun silk-like cocoon. Because it is sticky, the cocoon quickly becomes coated with environmental debris, which serves as a camouflage. Insecticides do not readily kill fleas that are still inside cocoons because the cocoon is usually inaccessible at the base of carpeting or pet bedding.
When the adult flea emerges from the cocoon, it immediately begins seeking a host for a blood meal. Adults orient and move toward light and prefer to move upward in direct contrast to the larvae. as a result, newly hatched fleas move directly to the top of the carpet pile, bedding material, or other surface, where they are more likely to encounter a passing host.