Fleas

Pest Management Fact Sheet #5020

James F. Dill, Pest Management Specialist
Clay A. Kirby, Insect Diagnostician

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Description & Biology

The flea most commonly encountered in Maine is the cat flea, Ctenocephalides felis. Although fleas are capable of transmitting diseases, this is rare in Maine.

Fleas pass through a complete life cycle: egg, larva, pupa, and adult. The tiny clear-to-white eggs can be seen without magnification. Eggs are laid on pets or other warm blooded hosts but may be found wherever they fall off from a flea-infested pet. Eggs and flea feces often accumulate where pets rest and this creates an appearance of mixed salt and pepper. It takes from one to twelve days for the eggs to hatch.

Upon hatching from their eggs, the eyeless, legless, whitish, maggot-like larvae seek protected areas in floor cracks, carpets, or in pets’ beds where they feed on organic material such as food crumbs, animal waste and adult flea fecal material. The larvae molt three times and mature in seven to 15 days. Unfavorable conditions such as dryness may extend the larval stage to over six months. The larvae often hide in moist sand and pet runways.

The mature larvae enter the pupal stage after spinning silken cocoons from their saliva mixed with other debris. In about seven days, the adult fleas are ready to emerge from their cocoons. Sometimes they rest in the cocoons until a noise or vibration indicates the presence of an animal or human. This is why severe flea problems are often noted after returning from several weeks of vacation or when moving into an empty house, as the fleas are primed for their very first blood meal by that point.

The female fleas (1/8″) are a bit larger than the males. Their narrow bodies (with bristles pointed backwards and long, spiny legs) can move forward quickly through fur, hair, feathers, and some loosely-woven fabrics. Their hind legs are adapted for jumping. Sucking mouthparts are used to obtain blood from the host, which could be a cat, dog, bird, human, or other warm-blooded animal.

It takes 27 to 40 days for the cat flea to complete one life cycle, or one generation. A female flea must have a blood meal before she lays her eggs, even though she has mated. A hot, dry summer reduces the number of fleas, whereas humid, rainy weather favors their increase. Environmental conditions greatly affect the length of a flea’s life. The average life of an adult flea without a blood meal is two months. But under hot and dry conditions, and still without a blood meal, an adult flea may live from only two to five days. Under more favorable conditions and with adequate blood meals, however, a flea may survive from one month to a year. Cat fleas can be found on wild animals or pets in favorable temperatures and humidity and therefore can be a continuous problem.

Pets are usually blamed for carrying fleas, but rats and mice can also be sources of fleas or causes of a continuing flea infestation. However, fleas can also survive in homes where there are only humans present. Some humans are unaffected by flea bites to the point where they can live with fleas and not be aware they have them. But most people are very sensitive to flea bites. Flea bites are most likely to be found on the feet, ankles and legs of people in flea-infested areas. The bites have a red halo around a small red spot, and may be swollen. Several over-the-counter medications may give some relief for flea bites.

Management

Recently, there have been comments about fleas becoming resistant to some of the insecticides used to control them. This may be true to some extent, but in heavy infestations, it is more likely that something is lacking from one’s control efforts or that mistakes have been made. It could be that an insecticide is not being used correctly, the life cycle is not being considered, or another source for the fleas has escaped notice.

When an infestation seems uncontrollable in the summer, there is usually sandy soil or a gravel driveway around the home. Sand and gravel are ideal environments for larvae, and this is why fleas are sometimes erroneously called “sand fleas.” Spraying the lawn or driveway 20 feet beyond the area frequented by people or pets is necessary.

Pets must be treated with an insecticide from the pet shop or from a veterinarian. Use and repeat these treatments as directed. Imidacloprid (Advantage®), lufenuron (Lufenuron Technical®), fipronil plus S-methoprene (Frontline Plus®), permethrin, pyrethrins, and flea collars are typically used. When selecting an insecticide, remember that a cat is likely to lick itself. Always check with your veterinarian first and follow label directions. Do not use dog flea products on cats and vice versa.

In the home, you may use your vacuum cleaner to remove fleas. After vacuuming avoid spreading the pests by sealing the vacuum cleaner bag in a plastic bag before disposing it. For light flea infestations, mist areas where fleas are likely to be found. Pyrethrins can be used, but they will primarily kill only the fleas that are actually sprayed on contact; they have little residual effect. Preferred outdoor insecticides are pyrethroids such as bifenthrin or permethrin, both of which have some residual effect. Less toxic options include growth regulators (methoprene and pyriproxyfen), insecticidal soap, d-Limonene, silica gel, pyrethrins, diatomaceous earth, and boric acid flea control products.

If considering the use of any of the available one-time-release aerosol bombs, vacuum to remove lint or dust from cracks or folds where the fleas can hide. Cushions from stuffed chairs should be removed before vacuuming. Throw rugs must be taken up off the floor. Make sure your pet’s bed or primary sleeping area is thoroughly exposed to the fumes or spray. Spacing clothes in the closets may also help. Do not enter a treated home for at least four hours to give the insecticide enough time to work. Follow label directions.

Bomb treatments may not kill insects that are in the egg or pupal stage, nor those inside deep cracks where the insecticide mist cannot reach. Any of the insecticides listed above available in an aerosol spray should be used as a follow-up to control fleas that may escape a one-time-release bomb. An additional treatment 10 to 12 days after the first treatment should kill new larvae and prevent newly-emerged females from laying eggs.

Using any of the commercial repellents can be used to avoid being bitten and to decrease the odds of carrying fleas home from infested areas.

When Using Pesticides

ALWAYS FOLLOW LABEL DIRECTIONS!

Pest Management Unit
Cooperative Extension Diagnostic and Research Laboratory
17 Godfrey Drive, Orono, ME 04473
1.800.287.0279 (in Maine)

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