Fleas pass through a complete life cycle of four stages from eggs, larva, pupa, adult. The eggs are small and white. The complete life cycle from egg to adult varies from two weeks to eight months. Generally, after two days to two weeks the eggs hatch into larva. Larvae are blind, avoid light, and take a week to several months to fully develop. They pass through three larval stages. Their food source consists of digested blood from adult flea feces, dead skin, hair, feathers, and organic debris. Pupa mature to adulthood within a cocoon woven by the larva to which dust, pet hair, carpet fibers, and other debris adhere. After about five to fourteen days adult fleas emerge from the cocoon. The alarm clock that awakens the adult flea may include the detection of vibration of pet or human movement, pressure, heat, noise, or carbon dioxide (a potential blood meal). Female fleas lay-up to twenty eggs per day and six-hundred in a lifetime.
Although fleas can live up to two months or one year without eating, they cannot survive or lay eggs without blood. Newly emerged adult fleas live only about one week if a blood meal is not obtained.