Understanding the Enemy: the Flea Life Cycle

Thanks to the flea control products available today, flea management is easier and more effective than ever before. Clients often do not realize the damage and irritation that flea infestations can cause their furry friends, as well as their own household. Understanding the fleas life cycle increases our ability to help our clients control their flea population.

Fleas are insects in the Siphonaptera order, meaning they have a siphon-like mouth and no wings. The life cycle is similar in almost all 2,200 species of fleas. Only a few species are problematic for pets.

Life Goes On

Adult fleas are ectoparasites that live outside their host; larvae live in the host's environment. Fleas are metamorphic, which means they undergo a marked change of form and structure as they grow from embryo to adulthood. Similar to butterflies, their development evolves from eggs to larvae to pupae to adulthood (in simpler terms, egg, caterpillar, cocoon, adult). Depending on their environment, it can take as few as 12 days and as many as 350 days for fleas to go through growth stages and emerge from the cocoons. At any given time, the flea population typically is made up of 50% eggs, 30% larvae, 15% pupae, and only 5% biting adults.

Optimum temperatures for fleas range from 70°F to 85°F, and optimum humidity is 70% to 80%. No flea at any life stage can survive several days in temperatures below 37°F. Most fleas spend winter as either adults on infested animals or as pupae in cocoons in areas protected from freezing. Flea populations typically increase about 5 or 6 weeks after warm spring weather begins and often escalate during the full in midwestern and northern states.

The female flea mates after feeding and begins producing eggs within 1 to 2 days after taking her first blood meal. Then she deposits half-centimeter-long white oval eggs (they resemble grains of salt) in a host animal's hair, and the eggs drop off onto bedding, carpet, or soil. A single female flea can lay up to 50 eggs in a day and about 2,000 eggs in her lifetime.

After 1 to 6 days, the eggs hatch into larvae that look like small white bristle worms with mouths that can chew: They are blind, long, and segmented and have white hairs. Larvae dislike sunlight and hide in dark places indoors and out, such as grass, soil, carpeting, sand, and gravel. Larvae ingest adult flea feces that contains dried blood, and they molt (or shed) twice within 9 to 200 days. They dry up easily and relative humidity less than 50% is fatal. Although the typical larval stage lasts 5 to 11 days, it can last up to 2 to 3 weeks if the humidity, temperature, and food availability are just right.

The larvae's third molt produces a whitish~ gray silken cocoon in which pupae develop within a week or two. Since larvae spin cocoons at the base of a carpet, under bedding or at the base of grass, they are protected from insecticides. Outdoors, larvae prefer shaded, cool, moist areas. Full-grown adults in the cocoon detect heat, vibrations, and exhaled carbon dioxide, indicating that a host is near. They can remain in the cocoon for weeks or months while waiting for a host. The adults then leave their cocoons, hop onto that nearby host, find a mate, and repeat the life cycle.

The adult female flea indulges in numerous meals daily; often feeding for up to 3 to 4 hours at a time; she can consume 13.6 mg of blood daily. Soon she begins laying approximately 150 to 300 eggs per week. She eats significantly more food than she needs, processing most of it into nutritious fecal pellets for her offspring. As you can imagine, a flea infestation can easily lead to an anemia condition in the host animal.

Free at Last

The newly freed adult flea will leap at any likely warm-blooded host. They prefer dogs and cats as hosts, but human ankles, ferrets or domesticated rabbits will certainly do in a pinch. Estimates indicate that for every adult flea found on a pet, about 100 fleas are developing in the pet's environment.

Adult fleas come out from the cocoon full size and seek a new host from which they can live for months. Newly emerged adult fleas can survive only about a week without a blood meal. Unlike most houseguests, adult fleas will not leave on their own free will and must be dislodged from their hosts. Grooming activities such as brushing and using a flea comb will dislodge the parasites.

Since many variables affect the fleas life span, the entire life cycle can last anywhere from 2 weeks to 6 months. In the typical home, however, fleas generally live for 3 to 4 weeks. Helping understand that both your pets and your home environment must be treated simultaneously will help them to successfully control flea populations at all stages of their life cycle.

Fascinating Flea Facts

  • The average flea is 2 to 3 mm long and weighs one-millionth of a pound.
  • Just four female cat fleas feeding four times a day for 100 days will bite a cat or dog 1,600 times.
  • Flea "dirt" is actually an adult fleas feces, which is rich in blood and serves as nutritious fecal pellets for her offspring.
  • Historians believe that the original job of "lapdogs" was to lure fleas off their owners and onto them!
  • Flea brides and grooms (dressed, but dead) were popular collector's items in the 1920s.

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