A flea emerges from an egg and undergoes complete metamorphosis before becoming an adult. The eggs of the cat flea undergo internal fertilization, though biologists do not know the mating habits of these insects. Fleas breed year-round.
The females lays eggs on the cat or other hosts, though they quickly fall into the cat's bedding and develop. At the right temperature, which is about 55 degrees Fahrenheit, the eggs hatch after about six days. A colder environment with low humidity delays hatching and overall development.
The larva molts three times, then spins a cocoon and pupates. Vibrations and the amount of carbon dioxide in the environment influence when the adult emerges from its cocoon. The cat flea's life cycle lasts between 30 and 75 days.