The life cycle of fleas consists of four stages: eggs, larvae, pupae and adult. While adult fleas account for the clinical problems fleas create, they represent the smallest percentage of a given flea population, with the pupae representing the next smallest percentage of the population. The majority of the flea population (more than half) in a given infestation consists of flea larvae, while flea eggs account for roughly one third of the total population.
While they represent the smallest percentage of a total flea population, they’re the main offenders. They’re are the ones doing the biting, mating and laying the eggs. Adult fleas emerge from their cocoons once they detect a host. Detection of a host is triggered by vibrations, body heat and even the carbon dioxide of an exhalation. Once a flea jumps onto a host, adult fleas feed, mate, lay eggs and start a new generation.
Don’t Egg Them On
Up to about 50 eggs can be laid each day by an adult female flea. The eggs, which have a pearly luster, are smooth and oval, comparable in size to a grain of sand, and are laid on the host's body (usually your pet’s back). The eggs are not sticky, so they’ll typically fall off of the host’s body, meaning that most of the eggs could end up in the locations the host spends the most time. Usually, in as little as 1 or 2 days or as much as 5 or 6 days, these eggs hatch into the larval stage.
The legless, whitish larvae use a spine atop their head to hatch. This spine is gone after the first larval molt. The newly hatched larvae travel away from light, which is why they might be found closer to your pet’s skin, beneath their hair, or in small crevices around the house. They survive by eating the feces of the adults. The blood meal that adults expel is commonly referred to as “flea dirt,” which feeds the larvae. Larvae don’t travel far from where they’ve hatched, and after their second molt, they spin their cocoons (usually over the course of several days), from which they grow into pupae.
You Say Pupa, I say Pupae
The pupal stage is one in which the larvae, encapsulated in cocoons, transform into adult fleas. Many cocoons will protect the transforming fleas within from pesticides and other chemicals. Although the pupal stage commonly averages from about 1 to 2 weeks, fleas can remain dormant in this stage for 12 months. The great disparity in determining the amount of time spent in the pupal stage is most often due to external conditions. If the temperature and humidity aren’t conducive to emerging for a meal, they’ll wait it out. When body heat or vibrations trigger the presence of a nearby host, they’ll emerge, marking the start of a new cycle.
As you can see, killing adult fleas only takes care of part of the problem. Controlling fleas in all life cycles is the key to avoiding a flea infestation in your home, yard or on your pet.
More on Fleas
What is Flea Dirt?
How to Use a Flea Comb?
Flea and Tick Season: When to Use What Treatment
What Diseases Do Fleas Cause?
What Does a Flea Bite Look Like?