Fleas undergo complete metamorphosis.The life cycle, or stages, of the flea is composed of the egg, larval, pupal and adult stages. Cycle length ranges from several weeks to several months and is largely dependent upon environmental conditions.

Eggs
Fleas lay between four to eight eggs after a meal, with the highest concentrations of laying occurring within the last few days of the female’s life. Unlike the eggs of some other parasites, flea eggs are not sticky and usually fall to the ground immediately upon being laid. Flea eggs hatch into larvae within one to 12 da ys.

Larvae
Flea larvae are approximately 3 to 5.2 mm long and are semitransparent white in color. The larval stage lasts from four to 18 days, after which larvae spin silken cocoons and enter the pupal stage. The pupal stage may be complete within three days, or it can last as long as one year.
Flea larvae hatch from eggs that were laid by a female flea and have fallen off the animal host. Once away from the host, the larvae seek out shaded locations such as cracks in the floor, in carpets, in pet bedding or protected locations under and in furniture. Flea larval survival depends on relative humidity and temperatures. Since dehydration is fatal to flea larvae, they will not survive relative humidity less than 45-50 percent or soil temperatures greater than 95 degrees Fahrenheit. However, if outdoor larvae will survive in cool, shaded areas and do very well in crawl spaces. In environments of suitable humidity and temperatures, fleas will develop year round.
Flea larvae complete three larval instars (stages) and, depending on their environment, will range in length from about 3-5 mm long. Flea larvae have no eyes and no legs. Their body is maggot-like and whitish, but turns progressively darker as the larvae feeds on feces excreted by the adult fleas. Other than feces, larvae will feed on various types of organic matter such as food particles, dead skin, dead insects and feathers. Flea larvae do not take a blood meal directly from a host, unlike adult fleas. The flea’s larval stage is completed within about 4-18 days. One of the last activities of flea larvae is to spin a silken cocoon and then enter the pupal stage.
Controlling flea larvae usually involves using vacuums to remove, use of insect growth regulators and dust formulations that cause desiccation of the larvae.

Adults
Adult fleas begin searching for food when they emerge from the pupal stage. While fleas are noted for their jumping abilities, they will remain stationery when a suitable host is located. Females begin laying eggs within 48 hours of the first feed, thus beginning the life cycle again.
Cold environments cause eggs to perish before hatching. Humidity below 45 percent will kill larvae. Fleas in the pupal stage will become adults more rapidly in the presence of warmth and high humidity.