Online Sources

All Experts Entomology

Canine Vector Borne Disease

Cat Blood Donors

Cat World

Chemical Land 21

Do It Yourself Pest Control

eHow "How Fast Do Fleas Multiply?"

Electronic Data Information Source

Extension Toxicology Network

Fleas Georgia

Host grooming efficiency for regulation of cat flea populations

Household Products Database of USDHHS

Integrated Pest Management

Living with Bugs

Medical Entomology

Micrographia "The Cat Flea"

National Center for Biotechnology Information (pdf)

National Pesticide Information Center

Pawprints & Purrs

The Pet Center

Pet Education

The Pied Piper


Seattle Alternative Veterinary Care Examiner

Sex Ratio in Flea Infrapopulation

Skyway Pest

Survey of flea Iran

Texas Agricultural Extension Service

U Missouri Extension

Vet Stop Pet Info

Veterinary Parasitology (pdf)

WVU Extension Service (pdf)


Flea Information

Flea Life Cycle, Flea Description, Flea Population Projections, Flea Insecticides and Medicine, Fleas on Cats, Ctenocephalides felis

This information was compiled July 17-20, 2010 by Su Leone for the purpose of putting all this information in one place online.

This information and references are provided from a cat owner's point of view, but can certainly apply to other pets.



All images are shown at actual size and 10x magnification. Thanks, Bayer Animal Health!

Female fleas (shown here in outline) are about half a millimeter bigger than males and typically begin to lay eggs 36-48 hours after mating, which they can do upon hatching from the cocoon if there is a fully fed male already on site. A single female lays about 15 to 25 eggs a day, at a rate of approximately one per hour. More females survive to adulthood, perhaps because they are bigger and therefore faster. Or maybe it's maternal instinct. Or maybe boy fleas are just stupider. Regardless, the ratio of male to female adult fleas is about 1:2.9.

Adult fleas thrive at temperatures between 66 degrees and 84 degrees F and at relative humidities between 70 and 90 percent. Fleas prefer moist areas that do not get flooded with water and are out of direct sunlight.

Adult fleas eat, poop, walk around and mate. They poop about 10 minutes after each blood meal, and it comes out in a spiral. If you see a tight brown spiral about 3/4 cm big where you cat was laying, that means there hasn't even been enough time for that spiral to break into pieces that we recognize as "flea dirt". Yes, a bug was just munching on your baby.


Time in Stage:
15-196 days

Life Cycle Day:
Day 1 and Day 16

% of Flea Population:
5% adults & pharates

Note the golden color. Yeah, that's because it hasn't drunk blood yet! It takes about 48 hours of feedings (about 20 blood meals) to be a fully fed “grown” adult.

Fully fed males can successfully mate with a newly hatched female. It doesn't work both ways.


Time in Stage:
1 day

Life Cycle Day:
Day 15

% of Flea Population:
5% adults & pharates

Silken cocoons are made of caterpillar spit and local debris. It's that camoflage which makes them next to impossible to spot.

The young fleas only take a few days to mature, then can lie dormant for up to five months, emerging when vibrations, heat and carbon dioxide in their vicinity signal the arrival of a potential new host. They then emerge within seconds and leap towards the source. 

The cocoons are extremely resilient to impact and chemicals, but are very sensitive to desiccation, essentially mummifying the flea inside.


Time in Stage:
5-140 day

Life Cycle Day:
Day 10

% of Flea Population:

Caterpillars do not live on a host animal, rather they develop at the base of bedding and carpet fibers, and in crevices near where the cat walks or rests. They avoid light.

Dried flea excrement and cat skin flakes also accumulate in these places, providing food for the flea larvae when they hatch.  They turn a reddish brown color when feeding on flea poop ('cuz it's mostly blood).

When disturbed, they curl up into a spiral. Like most caterpillars, flea larvae are the stage that is most sensitive to extremes in temperature and humidity. They are especially prone to drying out and will die at humidities
below 45 percent. Larvae will not grow or mature at temperatures below 55 degrees F or above 95 degrees F.


Time in Stage:
5-11 day

Life Cycle Day:
Day 5

% of Flea Population:

Eggs are laid by the female about 2 days after mating.

Newly laid eggs are 3mm wide ovals that are dry and smooth, so they fall out of the cat's fur into its surroundings -- carpet, bedding and other resting places. These are the "salt" part of the "salt and pepper flea dirt". Since the caterpillars aren't biters, the eggs are not cemented to the hair shafts like lice. Rather, they fall off to the same place as their food: flea poop, dead skin and other organic debris end up.

The lower the temperature, the fewer larvae will hatch. Eggs are sensitive to desiccation. Flea eggs don’t hatch if the temperature is below 40 degrees F. A temperature below 46 degrees F for 10 days or 37 degrees F
for five days will kill flea eggs. A relative humidity of less than 50 percent will reduce egg hatch by 20 to 60 percent.


Time in Stage:
2-5 day

Life Cycle Day:
Day 3

% of Flea Population:



1. Borax, Sodium polyborate or borate kills adult fleas and inhibits growth of immature fleas by interrupting nerve conduction. It is more toxic to pets than other insect growth regulators and insect development inhibitors. This readily available powder also dessicates eggs, caterpillars and cocoons. Products with eucalyptus oil and peppermint oil (such as foot powder) also kill, repel, and dessicate.

2. Diflubenzuron inhibits the production of chitin during pupation. It is slightly toxic, but has no long-term harmful effects on animals.

3. Dioctyl sodium sulfosuccinate, docusate and undecyclenic acid soften the waxy protective covering of chitinous insects, eventually causing damage to internal organs and death.

4. Fenoxycarb slows physical growth and molting, which prevents sexual maturity.

5. Fipronil is a general neurotoxin that is more likely to bind with insect neuro-receptors than animal neuro-receptors.

6. Hydroprene slows physical growth and prevents sexual maturity.

7. Imidacloprid is a synthetic derivative of nicotine called a neonicotinoid. It is neurotoxic in insects such as fleas and honeybees, and can kill by contact or ingestion of treated crops or animals.

8. Lufenuron is stored in the body fat of animals which is then ingested by the biting insect. It prevents the formation of chitin during pupation.

9. Metaflumizone blocks insects from using sodium, which causes paralysis and death. It is relatively safe to use around mammals.

10. Methoprene is an insect growth regulator that is used in insecticides and in the production of a number of foods including meat, milk, eggs, mushrooms, peanuts, rice and cereals. It not only kills some caterpillars, but if they survive to spin a cocoon, the flea will die within it.

11. Moxidectin is a general neurotoxin, which can affect animals as well as insects. If your pet shows neurological symptoms, stop using this product immediately and call your veterinarian.

12. Nitenpyram is a synthetic derivative of nicotine called a neonicotinoid. It is neurotoxic only to adult insects.

13. Piperonyl butoxide is a synergist that enhances the pesticidal properties of other chemicals. It is derived from safrole, a constituent of the sassafras fruit. It is not vey toxic to mammals.

14. Pyrethrins  are natural compounds found in the chrysanthemum plant. They are water soluble and are degraded by stomach acid, so toxicity is rare. They are a neurotoxin that kills by interrupting neural transmission resulting in seizures, then paralysis and death.

15. Pyrethroids are synthetic pyrethrin compounds that are slower to act than natural pyrethrins, but last longer. Examples are allethrin, resmethrin, phenothrin, etofenprox, and permethrin (which is toxic to cats).

16. Pyriproxyfen mimics insect juvenile hormone, which prevents the caterpillars from going through their final molt which prevents pupation.

17. Selamectin is a neurotoxin that causes paralysis and slow death. The insect is affected by ingesting the chemical.

18. Tetramethrin is a neurotoxin.





I have run a series of mathematical projections based on what I have learned about fleas and flea treatments. I have established assumptions derived from my reading of the sources listed in the sidebar. Here are the assumptions upon which my projections are based: