Life cycle of fleas makes them difficult to control indoors, outdoors

Every year several homeowners experience flea problems – inside or outside the home and sometimes both. Flea control can be one of the hardest battles to fight when it comes to controlling these insects both indoors and outdoors.


A lesson in the life cycle of fleas will help you understand why they are so difficult to control. Fleas have what we call a complete life cycle. The egg is whitish, about 1/32 inches long (about the size of a period at the end of a sentence). They are laid on the host (dog or cat or even you!) and fall to the floor, ground or on furniture and then hatch in usually 2-3 days.

The eggs hatch into a larval stage. Larvae are very small, white and mostly translucence. They look like tiny worms with sparse hairs on the body. At 80 degrees, it takes three to four weeks for fleas to develop from egg to adult. Moisture also plays an important role in larval development. The relative humidity has to be above 50 percent. There is usually sufficient humidity inside a house to complete the development. Outdoors can be a different matter, though. In dry weather fleas might only survive in cool, damp areas.

Larvae feed mainly on undigested blood voided by adult fleas. The blood dries on the hair and falls from the animal. This is what we commonly call the “flea dirt.” This is important to know because the adult fleas live their entire life (for the most part) on dogs and cats. So where these pets spend most of their time is where most of the eggs and larvae are going to be found.

Larvae then hatch into the pupal stage. The pupae are found within a silken cocoon, which is covered with sand, dust or other organic debris. Because of this covering, the pupal stage is nearly impossible to kill with insecticides.

Under favorable conditions, adult fleas emerge in a week or two, but in the absence of a food source, they could remain in the cocoon for as long as six weeks. The fact that adult fleas can live without food for remarkably long periods accounts for situations where people might enter a house after it has been unoccupied by humans or pets for several weeks yet be rapidly and severely attacked by fleas.

The secret to good flea control is to treat before the fleas get started. First, you always start with the pet. Make sure you are using a good preventive flea treatment such as Frontline, Advantage, or K9 Advantix.

A problem with flea control inside and out is insecticides only kill adult fleas and adult fleas are only about 10 percent of a flea population. The other 90 percent are the other life stages I mentioned earlier: eggs, larvae and pupae. So when you use insecticides, you are killing adult fleas but not the other life stages. In about a week, your flea problem comes back. The key is to use an insecticide growth regulator mixed with the regular insecticide such as carbaryl (Sevin), malathion or a pyrenthrin (bifenthrin, cyfluthrin, lamda-cyhalothrin, etc.). The growth regulator will kill all four life stages, though not that good on the adult stage which is why you want to mix it with a regular insecticide. There are several growth regulators such as methoprene (Precor), pyriproxyfen (Archer), and cypermethrin (Viper). Probably the only one you will find in the Augusta area is Viper, and there might be only a few places that carry it. You will probably need to check garden centers and feed and seed type stores.

Depending on the size you buy, the Viper can be used indoors and outdoors. The one ounce is normally designed and labeled for indoor use. Obviously one ounce mixed in a gallon of water won’t go very far outdoors. By using this and mixing it with a regular insecticide, you should be able to control fleas for three to four weeks, if not longer, instead of just one week. The main thing you are trying to accomplish is to break that life cycle and cut down on the numbers.

Outdoors, treat grass and soil areas where the pet spends a lot of time. This is usually in shaded, moist areas around the dog house and beneath shrubbery. You will probably have few, if any fleas, in open areas that get a lot of sun. The fleas just cannot survive there.

If you use this growth regulator indoors, you should knock out your flea problem 100 percent. Treat the floors, especially carpet, furniture and cushions in areas frequented by the pet. And be sure to treat under beds and furniture.