Fleas remain close to their hosts, living in their nests and homes, preferring warm humid sites.
The cat flea is the most common household flea in the U.S., and it's preferred hosts are cats, dogs and people. The eggs are not fastened to the host, but may be laid in small batches on the host, nearby in the host's nest, or in dirt and lint. In one to twelve days the eggs hatch into maggot-like larvae that feed on dirt and debris, including dried blood from adult flea droppings. After seven to fifteen days the larvae spin silken cocoons, usually covered with debris for camouflage, and become pupa. Adult fleas emerge from the cocoon in a week, or they can delay emergence as long as a year if conditions are unfavorable.