How Long Is the Flea Cycle?

The flea life cycle begins when the female flea lays her eggs in the hairs or feathers of the host animal. Fleas lay about 50 eggs at one time, but a female might lay batches of eggs totaling 2,000 or more over her lifetime. The eggs fall off the host animal, into the soil if outdoors and onto rugs and furniture if inside. Within 12 days, the fleas hatch into larvae. Some species of fleas hatch earlier -- within a week -- in warm temperatures.

Tiny, white flea larvae feed on adult flea feces, the infamous dried blood of "flea dirt" you might find on your infested cat or dog. If flea dirt isn't available, larvae feed on any available decaying organic materials. Very hot temperatures can destroy the larvae. The larval stage lasts two weeks or less, after which the worm-like creatures spin a cocoon and enter the pupal stage.

Technically, the pupal stage doesn't last that long. Within one to two weeks, the pupa becomes an adult. However, it might not leave its cocoon even though it has matured. It must latch on to a passing host before leaving the cocoon. The adult flea can live within the cocoon for up to five months before it ends up on a bird or mammal. It takes just a few seconds for the adult flea to emerge from the cocoon when a potential host appears. Fleas flock to the animal's body heat and movement.

Brown and wingless, the adult flea is only about 1/8-inch long. Before fleas can mate and start the next flea cycle, they require a blood meal. As soon as they land on the host, they begin biting. Reactions to the saliva the adult injects into the bite causes the violent itching experienced by victims. Once the female has her meal, she starts laying eggs within two days. In a best-case scenario for the flea, and a worst-case scenario for the victim, an adult flea can live on a host for two months or more.