Fleas are holometabolous insects, going through the four life cycle stages of egg, larva,pupa, and imago (adult). Adult fleas must feed on blood before they can become capable of reproduction.
The flea life cycle begins when the female lays after feeding. Eggs are laid in batches of up to 20 or so, usually on the host itself, which means that the eggs can easily roll onto the ground. Because of this, areas where the host rests and sleeps become one of the primary habitats of eggs and developing fleas. The eggs take around two days to two weeks to hatch.