When the host is removed for a period of time, they are left without food. Hungry adult fleas often attack the first warm blooded animal that comes in the door, often biting people around the ankles. In addition to adult fleas present at the time, vibrations are known to cause, at least in part, the emergence of new adults from pupae. Walking across the floor may trigger emergence. Adult fleas live on the blood of the animals, and must have a blood meal to reproduce.
Female fleas lay eggs, usually on the host, after taking a blood meal.
The eggs, however, are not attached to the host and shortly fall off and develop on the ground or in the host's nest or resting place. They have a well developed head capsule with chewing mouthparts. Thus they are often found in pet resting places. Larvae tend to avoid light by burrowing down into carpeting or hiding under pet bedding. They jump quickly onto the host and begin feeding.