fleaFleas – Adult fleas are wingless, brown to black insects about 1/16 inch long. Fleas mate on the pet, and both sexes bite. After each blood-meal, the female usually lays four to eight eggs. Over her lifetime, a female may lay more than 400 eggs. Flea eggs are smooth, whitish, and oval and readily fall to the floor or ground from the pet. Depending on temperature and humidity, flea eggs hatch in one to ten days. Newly hatched fleas are minute, slender, whitish, wormlike larvae. The larvae avoid light, burrowing into carpets, cracks, or, if outdoors, soil. The larvae spin silken cocoons. These are hard to see because fleas incorporate nearby debris into the cocoon. The cocoon protects the developing flea from insecticides. Fleas can stay in the cocoon for periods ranging from less than a week to more than four months.

Adult fleas emerge from their cocoons after a physical disturbance or in the presence of warm-blooded animals. This is why vacationers often return to find their homes overrun by fleas. The adult fleas remain in their cocoons when the house is quiet, emerging hungrily all at once when the family returns.