The eggs have smooth shells and are not stuck to the host, so they roll off into the host's surroundings. Adult fleas that have taken a blood meal will excrete partially digested blood in their feces. Smooth-shelled eggs that roll off of host along with partially digested blood that will become larval food source. The egg stage is easily vacuumed up and discarded. Flea larva that will feed on the partially digested blood excreted by adults.
Fleas use whatever material they are living in to make the cocoon.
Blue carpet fibers will result in a blue cocoon. Fleas are most protected from traditional insecticides during the pupal stage. Fleas develop into adults and remain in their cocoons until conditions are conducive to successful reproduction. One female cat flea can lay between 158 to 420 eggs in her lifetime. Some estimates are higher.