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The Life Cycle of the Flea
6 years ago
| Blue Label
Understand fleas so you can get rid of them on your pet and in your house

By Janet Tobiassen Crosby, DVM, Guide

Anatomy of the flea © Al2 on Wikimedia Commons

Anatomy of the flea

© Al2 on Wikimedia Commons

Fleas. They make pets' lives miserable, and humans begin to itch just at the thought of them. Vets are often asked what pill, drug, dip, collar, or shampoo works the best to get rid of these persistent parasites. The answer is there is no single method or insecticide that will completely eradicate (or at least control) a flea problem.

     Please stay tuned for the next installment.....

6 years ago

Part I of this article is to give some insight to the biology of the flea. Why go back to biology? Because the flea life cycle is fairly complex, and understanding the various stages will make it easier to get rid of fleas. Part II of this article will discuss why multiple approaches are needed to control/eradicate fleas.

The life and life cycle of the flea

There are many hundreds of species of fleas. Collectively, all of the species of fleas are categorized under the order name of Siphonaptera. The cat flea, Ctenocephalides felix, is the most commonly found flea in the US and infests cats, dogs, humans, and other mammalian and avian hosts.

6 years ago

Fleas thrive in warm, moist environments and climates. The main flea food is blood from the host animal. Host animals are many species - cats, dogs, humans, etc. Fleas primarily utilize mammalian hosts (about 95%). Fleas can also infest avian species (about 5%). Flea saliva, like other biting skin parasites, contains an ingredient that softens, or "digests" the host's skin for easier penetration and feeding. The saliva of fleas is irritating and allergenic -- the cause of all the itching, scratching, and other signs seen with Flea Allergy Dermatitis, or FAD.

Fleas have four main stages in their life cycle: egg, larva, pupa, and adult. The total flea life cycle can range from a couple weeks to several months, depending on environmental conditions.

6 years ago

ADULT: The adult flea is very flat side to side. There are hair-like bristles on the flea body and legs to aid in their navigation through pet hair. Fleas have 3 pairs of legs, the hindmost pair designed for jumping. Fleas are well known for their jumping abilities. Click here to learn more about flea anatomy.

Adult fleas prefer to live on the animal and their diet consists of blood meals courtesy of the host animal. The female flea lays white, roundish eggs. The adult female flea can lay up to 50 eggs per day1, 500-600 eggs2 over several months.

6 years ago

EGG: The eggs are not sticky (like some parasites), and they usually fall off of the animal into the carpet, bedding, floorboards, and soil. When the flea egg hatches varies -- anywhere from two days to a few weeks, depending on environmental conditions. The larva emerges from the egg using a chitin tooth, a hard spine on the top of the head that disappears as the flea matures.

LARVA (plural = larvae): The larval stage actually has three developmental stages within this stage. Larvae are about 1/4" (6.35 mm) long, and semi-transparent white. They have small hairs along their body and actively move. They eat the feces of adult fleas (which is mostly dried blood) and other organic debris found in the carpet, bedding, and soil. Depending on the amount of food present and the environmental conditions, the larval stage lasts about 5 to 18 days (longer in some cases) then the larva spins a silken cocoon and pupates.

6 years ago

PUPA (plural = pupae): The pupa is the last stage before adult. The adult flea can emerge from the cocoon as early as 3 to 5 days, or it can stay in the cocoon for a year or more, waiting for the right time to emerge. When is the right time? (Never, say pet lovers everywhere!) Stimuli such as warm ambient temperatures, high humidity, even the vibrations and carbon dioxide emitted from a passing animal will cause the flea to emerge from the cocoon faster. This brings us back to the adult flea.

The entire life cycle is quite variable, as evidenced by the variability in each life stage progression. As mentioned above, the cycle can be as short as two weeks or as long as two years. That is why it is so important to remain vigilant, even when a flea problem is thought to be under control! The duration of flea season varies with location.

6 years ago
In Part Two of this article, various methods of flea eradication will be discussed, both for the pet(s) and for the environment.

Ready to test your knowledge of fleas? Take the Quiz!

6 years ago
Part I of this article discussed the biology of the flea. Understanding the various stages of the flea life cycle will make the various flea treatment regimes easier to understand and apply. The purpose of part II of this article is to demonstrate why multiple approaches are needed to control/eradicate fleas.
6 years ago
Flea control on your pet

This is where most pet owners focus first - getting those fleas off of the beloved pet. The constant scratching, biting, and licking are bothersome on their own, and it is not healthy for the animal's skin, either. Flea Allergy Dermatitis, or FAD, is a common reason for veterinary visits all year-round in some areas.
6 years ago

A mistake seen all too often is the "more is better" approach that some people take. More is NOT better when it comes to chemicals or medications! Following package directions is essential when using over the counter products and medications. Only buy products that are labeled for use on the species you will be using them on (dog, cat, etc.). Cats in particular are very sensitive to drugs and chemicals - be sure to read all labels carefully.

Even when labels are read and instructions are followed, adverse reactions to flea product can happen. Call your vet immediately. Other resources are Animal Poison Control Center and Adverse Drug Reporting hotlines.

6 years ago

Shampoos and dips

A shampoo, or "flea bath" is a good first attack on fleas for the pet that has large numbers of fleas visible on its body. Cats can be difficult to bathe. It is important to know how to properly use the medicated shampoo to effectively rid your pet of fleas. It is also important to realize that a flea shampoo is not intended for lasting control. Many people are surprised when they see fleas and it was "only a week ago" that the pet had a flea bath. Shampoos are only effective for a day or less. They leave little residual chemical on the animal when properly used.

6 years ago

Flea dips are strong chemical rinses to rid animals not only of fleas, but mites and ticks as well. I do not recommend dips unless absolutely necessary, as in the case of a mite infestation. Dips last approximately 1-2 weeks. That is a lot of chemical residue to leave on an animal! Flea shampoos and dips are effective for adult fleas.

Flea collars

Flea collars work one of two ways - by emitting a toxic (to fleas, anyway) gas, and by being absorbed into the animal's subcutaneous fat layer. The toxic gas is usually only effective in the immediate area of the head and neck. This type of collar is best used in the vacuum cleaner bags to kill any fleas vacuumed up. The collars that absorb into the subcutaneous fat are much more effective. Ask your vet what collars they carry. Collars are not for all pets - particularly cats that roam outside.

6 years ago

Flea collars are effective for adult fleas. Some collars have an IGR, or Insect Growth Regulator, to prevent flea egg and flea larval development as well.

Flea powders and sprays

Flea powders and sprays offer short term (2-3 day) protection from fleas, and with some products, ticks and mites too. Powders and sprays have fallen out of favor recently with the newer spot-on treatments that are available.

6 years ago

Most flea powders and sprays are only effective for adult fleas, some offer additional flea protection by inhibiting flea egg and larval development (contain an IGR).

Spot-on treatments

Common brand names include: Advantagetm, Frontline®, and Bio-Spot® just to name a few. These products are applied between the shoulder blades of the pet, and typically last about one month.

6 years ago

Spot-on treatments are effective for adult fleas. Some include ingredients to inhibit the larva from emerging from the flea egg and some are active against larval development as well. Click on the product names above to learn more about each individual product from the manufacturer's web site.

Oral medications

Flea "pills", such as Program® and Sentinel® work by stopping the larva from emerging from the flea egg. Program® is also available as an injectable medication for cats. Fleas ingest the blood of animals on these medications, and the female fleas then lay eggs that are unable to hatch. They do NOT kill adult fleas. These medications are essential to break the flea life cycle and stop the flea problem when used in conjunction with flea adulticide treatments.

6 years ago

Flea control for your house and yard

Flea control doesn't stop after your pet has been taken care of! Only about 10% of the flea population (mainly the adults) are on your pet. The flea eggs, larvae, pupa, and the few adults that reside in the carpeting, bedding, and living areas make up approximately 90% of the flea population. Neglecting this population of fleas will ensure that the flea problem will continue and worsen over time.

6 years ago
Diatomaceous Earth (DE) for Flea ControlHow DE works to controls fleas in the house and yard

By Janet Tobiassen Crosby, DVM, Guide

6 years ago
What is Diatomaceous Earth?

Diatomaceous Earth (DE) is a fine flour-like powder, the microscopic remains of fossilized diatoms, a type of algae. Diatoms are found in freshwater and saltwater. Capable of photosynthesis, they are an important food source for many organisms in these water ecosystems.

Diatom cell walls are made of silica, a component of glass. DE has been used for years as an insecticide to control mites, fleas and other insects; find out how it works here.

6 years ago
How Diatomaceous Earth Works to Kill Fleas and Other Insects



Fleas and other insects with an exoskeleton (hard shell) are susceptible to the glass-sharp edges of the microscopic diatoms. The silica shards cut through the waxy exoskeleton surface, effectively drying out the flea, resulting in death to these types of insects and their larvae.

6 years ago
Diatomaceous Earth Pros and Cons




  • The good news is that Diatomaceous Earth is non-toxic to humans and animals; it is even used in some foods food (food-grade quality, not the DE used for pool filtration systems) and some health supplements. DE is also used for a variety of beauty and health care products.
6 years ago
  • Daily vacuuming is an important component of household flea control. Diatomaceous Earth can be used safely on many surfaces and floor coverings, vacuuming up the DE after allowed to sit for at least a few hours or overnight. A few days, if doable.

  • Diatomaceous Earth is safe to use on pet bedding, in addition to weekly washing of pet bedding in warm water.
6 years ago
  • Diatomaceous Earth is safe to use around the yard, but large amounts may be necessary to have a positive effect on flea control. Regular mowing and trimming of vegetation also helps. For serious flea infestations of yard and garden, a consultation with a pest exterminator is in order.


  • Diatomaceous Earth is not toxic, does not have any residual problems, and because it is a mechanical killer versus a chemical killer, resistance to DE is not a problem.
6 years ago




  • Diatomaceous Earth is a very fine, silky powder; similar to flour or talc. It is messy and may irritate eyes and throat. Use caution and wear a face mask when applying. Food grade DE is ok to ingest, so it is not toxic to pets or people, but may be temporarily irritating.
6 years ago
  • Diatomaceous Earth that is used for pool filtration systems is very finely ground and is dangerous to breathe in. It is not recommended for flea and insect control.

  • Diatomaceous Earth must be dry to work. Wetting it down or trying to mix it with water to spray it and not breathe in dusk negates the useful action of DE. Always where a mask when applying DE.
6 years ago
  • Some advocate using Diatomaceous Earth directly on pets. Caution is advised if you elect to use it on your pet. Use food grade DE only. DE is very drying - it may dry out your pet's skin. Protect your pets eyes, nose, mouth when applying.


Fighting Fleas


Fleas are a pain to deal with, for pets and people. Fighting fleas effectively necessitates knowing about the flea life cycle and addressing fleas both on the pet(s) and in the environment.

6 years ago

Diatomaceous Earth is a safe and effective add-on to an existing plan or as a standalone flea fighter. There are many flea treatments available, depending on the severity of the problem, the climate, and your pet's overall health. Your veterinarian can help tailor a flea-fighting plan specific to your needs.

Some Tips: Daily vacuuming - this is very important for picking up adults, eggs, larvae and pupae before they develop. Putting a flea collar in the vacuum bag and emptying the bag frequently are also important; otherwise, the fleas will hatch, develop, and leave the vacuum to re-infest the living quarters. 

6 years ago

Wash all bedding, clothing, and removable furniture covers.

Apply insecticide - over the counter fogger or by a professional exterminator, such as Orkin. Follow all instructions very carefully, remove all pets, people, and cover all food in the environment before applying insecticide, and make sure everything is dry and it is safe to return according to package directions. Take special precautions for pets and children - eating or putting items in their mouth, etc.


     (Use only Natural flea Killers, because the Insecticides are Poisonous!)


Text: Copyright © Janet Tobiassen Crosby. All rights reserved.


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