Fleas are tiny reddish brown insects measuring about 1/6-inch in length and are laterally flattened.

Their flat shape allows cat fleas to easily pass between the hairs of animals. The cat flea is the species involved in most home infestations and will attack both cats and dogs. It is usually carried into the home by a pet. Once inside, large populations can build up quickly.

One female flea can lay about 18 eggs a day and just 20 fleas on a dog can produce 360 eggs per day and over 2000 eggs in a week. After the home is treated, it may take up to two weeks or more before fleas are no longer seen. The reason for this is that flea pupae are unaffected by the treatment until the adult fleas emerge from their pupal cocoon. In any flea population, all stages of the flea will be present including numerous pupae. It will take several weeks for all adult fleas to emerge from these pupae and contact the pesticide. Vacuuming as often as possible both before and after the treatment can speed up this process because it stimulates adult fleas to emerge from their cocoons.