The Scourge of Spring (and Summer and Fall), Part 1

The arrival of spring brings certain inevitable occurrences:  April showers, May flowers, and unfortunately fleas.  While fleas can live indoors year round, the heat and humidity that typically accompany spring are the perfect environment to spur fleas out of their ‘hibernation’ through the winter months and continue developing into the adults that make our pets itch and our skin crawl thinking about them.  It is important to understand how to eliminate the scourge of spring by first knowing the flea life cycle and the survival protections it offers, then learning techniques to decrease the immature stages in the environment, and finally outlining the various flea treatments available (focusing on products used in or on the animal) and how and on what stage of the flea they work.flea-life-cycle.png

There are four stages of fleas, of which the adult is likely the only one most people have ever knowingly encountered.  The adult flea is an insect, and like a butterfly emerges out of a hard cocoon, or pupa, in which it develops from the worm-like larva to the 6-legged adult.  This adult flea is the only stage that lives on the dog and, through its feeding and subsequent excretion of digested blood in its feces, is responsible for feeding the larval stage a blood meal to facilitate its development into the pupa. The larvae live in carpet fibers, cracks and gaps in hard surface floors or basically anywhere the pet can access. Immature fleas especially coalesce in the pet’s sleeping quarters including couch cushions, bedsheets, or anywhere the developing flea can avoid direct sunlight. Examples include under the recliner or under the bed, theirs or yours.  The larvae remain until they eat a blood meal sufficient in nutrients to transform from larva to adult in the pupal (cocoon) stage. The adult flea is also responsible for producing the next generation of fleas by laying eggs, It lays the eggs while feeding amongst the forest of hairs but the eggs fall off the dog as they get up to meet you at the door, change positions during sleep, or scratch at the fleas crawling on them.

To summarize, the adult flea begins laying eggs within hours after emerging and beginning to feed, and these eggs account for 50% of the total flea population. The eggs hatch into larva in as little 1 to 10 days after being laid but can lay dormant if the temperature and humidity aren’t right.  Larvae make up 35% of the total flea population. In as little as 5 days and as long as 6 months the larvae are protected as pupae wherein they undergo the change from larva to insect. This developmental cocoon, or pupa, is practically impenetrable and comprises 10% of the flea population.  Those pupa develop into adult fleas in as little as 5 days making the total life cycle as short as 14 days given optimum conditions or as long as 3-6 months. Adult fleas make up just 5% of the total flea population.


Of the immature stages of the flea, the egg and larvae are susceptible to varying forms of insect growth regulators/inhibitors, and insecticides.  Some people are concerned about these products with children or with pets that sleep with them and look for other ways to reduce the number of eggs that reach adulthood.  Some of these ways include regularly bathing your dog.  Even if you don’t use an insecticide, bathing helps you to see the numbers of adult fleas still remaining so you can assess how the program is working, as well as reducing the eggs not yet fallen off the dog.  In addition, regular vacuuming also removes a portion of the eggs and larvae from the environment.  It is additionally helpful to follow vacuuming with a steam cleaning of the carpet which helps to remove pupa as well.  Washing any bedding in hot water and drying on high heat can also make a big impact in reducing flea numbers.

In Part 2 of our Scourge of Spring series,we will discuss the overwhelming number of flea products, both topical and oral available for dogs and briefly cover how they work and where in the life cycle they are effective.