Fleas are pests of humans and their domestic animals all over the world. While most fleas prefer nonhuman host, many can and do feed readily on humans when infestations are heavy or when other hosts are not available. Adults fleas have piercing-sucking mouth-parts to penetrate the skin of the host and suck blood. Fleas have a complete metamorphosis. They are frequently laid on the host animal but may be laid by adults that have fallen to the ground (e.g., into carpeting or the host’s bedding). Since flea eggs are not attached to the host, those laid on the host will fall off and hatch on the ground, in nests or bedding, or in carpets, upholstery, or cracks in the floor. A female flea will lay a few eggs each day until she has laid up to 200 to 400 eggs will hatch in anywhere from 2 days to a week, but most will hatch within 2 to 3 days under favorable conditions.