Fleas in the pupal stage are resistant to all insecticides. They lie dormant in the cocoon from one week to one year. Stimulated by vibration, pressure and movement of nearby pets or people, body heat, or exhaled carbon dioxide, adult fleas emerge from the pupal stage, and immediately jump on a host in anticipation of a blood meal. They spend all of their time on the animal, feeding on blood. Adult fleas feed by piercing the skin with their mouth parts, sucking blood.
Flea bites can cause intense irritation and some animals become allergic to flea saliva.
The life span of the uncontrolled adult flea on the pet can range from 4 to 12 months, depending on grooming behavior of the animal. After ingesting their first blood meal, fleas reach their sexual maturity. They copulate and females begin laying eggs. Over the female's lifetime she can lay up to 2,000 eggs. Adult cat fleas are permanent ectoparasites on the host because they are unable to survive more than a few days without a blood meal.