A flea’s life cycle can be broken down into four parts: egg, larva, pupa, and adult. The adult lays eggs on a host, which then roll off into the environment. When these eggs hatch into larvae, the larvae hunker down in the environment, feed, and go through several molts until they spin a cocoon and become pupae. Eventually, from the pupae emerge adult fleas, which then seek out an animal host for a blood meal. Under ideal conditions, this entire process takes about 21 days. However, fleas have a very flexible life cycle, and will wait until conditions are optimal to move from one stage to another. “The more warm and the more moist it is, the faster the life cycle will go,” says Dr. Ann Hohenhaus, a staff doctor at NYC’s Animal Medical Center, who specializes in small animal internal medicine and oncology. “If it’s cooler and dryer, the process slows down until the temperature goes up.”
