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The Flea Life Cycle

Learn How Fleas Live Before You Treat an Infestation


An adult cat flea (male).

An adult cat flea (male).

K. Walker, Museum Victoria (Creative Commons Attribution 3.0 Australia License)

In order to control fleas effectively, you must understand the flea life cycle. Though there are several species of fleas that can infest your home, by far the most common species found on cats or dogs is the cat flea (Ctenocephalides felis), so I will focus on cat fleas in this article.

Fleas undergo complete metamorphosis with four stages: egg, larva, pupa, and adult. Environmental variables influence the length of each developmental stage. Fleas prefer a warm, humid environment, with temperatures ranging between 70° and 90° Fahrenheit and a relative humidity of 75% or more. Under ideal conditions, the cat flea life cycle takes just 18 days, from egg to adult.

Adult fleas (both male and female) require a blood meal prior to mating. They prefer blood from your pet, but in the absence of a canine or feline host, fleas will bite people.

Once mated, the female flea may deposit up to 50 eggs per day on your dog or cat. An adult flea typically lives for several months, so just a single flea can cause a significant infestation in a short amount of time. As your pet walks around your home, many of the flea eggs fall off. Cat flea eggs are tiny, measuring a mere 1/32 inch, so they can go unnoticed in your pet's bedding, in carpets, or on upholstered furniture.

Within 2 to 5 days, wormlike larvae emerge from the eggs. Lacking eyes and legs, you might think that flea larvae would have a tough time surviving in your carpet. But flea larvae do just fine hunkered down between the carpet fibers, where they feed on anything organic, from hair to adult flea excrement.

The larvae feed and molt for 1-2 weeks, and then pupate within silken cocoons. The flea cocoon is often camouflaged with debris, including hair, skin particles, and carpet fibers. In a warm environment and with your cat or dog available for a blood meal, the adult may emerge in about a week. The new adult flea will jump on your pet when he passes by, and immediately begin feeding on his blood.

You might think you can beat a flea infestation by simply removing your pet from the home for a while. After all, no host, no parasite, right? But fleas are clever pests. A fully formed adult flea can sit tight inside its cocoon for a year, just waiting for a host animal to reappear. The fleas stay safely in their pupal cases until they sense vibrations that suggest an animal is moving nearby. Like many insects that feed on blood, they can also sense an increased presence of carbon dioxide, which signals that a host is in the area.

So as soon as your dog or cat returns, the adult fleas will emerge and feast. And remember, they'll gladly feed on your blood if your pet is unavailable, so unless you are prepared to abandon your home for a year, you really must treat for fleas.

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