A flea passes through four stages to become the blood-sucking parasite he is. The entire cycle can last as short as a few weeks or as long as months, depending on the environmental conditions. PetMD states the ideal conditions for flea propagation are temperatures ranging between 70 and 85 degrees Fahrenheit and 70 percent humidity. An adult flea can live up to two weeks without a host.
Eggs: The First Stage
A female flea must have a blood meal from her host -- such as your cat or dog -- before she's able to lay her eggs. She's a productive parasite, laying up to 40 eggs in a day. She lays her eggs where she feeds -- in your pet's fur -- and eventually the eggs drop from your pet's coat as he goes about his daily routine. Eggs can hatch as quickly as two days or take as long as two weeks, depending on the environment. They hatch quicker if it's warm and more humid.
Larvae: The Second Stage
When the eggs hatch, blind larvae emerge and survive eating organic material such as dead skin, flea egg shells, adult flea feces and other debris. Larvae won't develop in sunny places, such as outdoors in an open, grassy area. Instead, they require cool, dark spots, such as shaded areas outdoors and in baseboards and in carpeting indoors. Their development depends on temperature and humidity. Generally, a flea will spend between 5 and 20 days in the larval state.
Pupae: The Third Stage
The larvae won't make it to the pupal state if the humidity is less than 50 percent or the temperature exceeds 95 degrees Fahrenheit. Otherwise, the adult flea remains in his cocoon waiting for the right conditions to emerge. A flea may emerge within days or, depending on the species, may wait weeks or almost a year to appear. When a potential host passes by, such as a person, dog or a cat, the flea is alerted to its presence through vibrations, body heat and increased carbon dioxide. The flea can emerge within seconds to jump onto its potential host.
Adults: The Final Stage
Generally, adult fleas bite humans but don't feed on them unless they're of a species that specifically feeds on humans, such as Pulex irritan, or the human flea. A flea must feed on its host within a few hours if it's going to survive. If the flea emerges and doesn't find a suitable host, or if it's dislodged from its host, it can survive as little as a few days or as long as a couple of weeks.
When a flea finds an appropriate host, it will begin feeding almost immediately. A female flea will begin laying eggs about 24 hours after enjoying her first blood meal. Fleas pass their time on their host eating, breeding and laying eggs. Usually, an adult flea will live for two or three months.
Fleas are more than irritating; they can cause tapeworm as well as flea allergies in pets. Understanding the flea's life cycle empowers you to keep you and your pet flea-free. A variety of flea preventive products on the market provide flea control for different stages of the flea life cycle. Topical spot-on and oral medications are formulated to kill adult fleas and some include ingredients to keep eggs from hatching and kill larvae and pupae.
Washing pet bedding in hot water will eliminate eggs, larvae and pupae and repeated, thorough vacuuming of rugs, furniture, cushions, beds and baseboards will remove some eggs and larvae. Discard the vacuum bag as fleas can live on inside the bag to re-infest. While good housekeeping is important, ensuring your pet isn't a hospitable environment is your best defense against fleas.