What do fleas eat? It is an interesting question where the answer depends on what life stage they are in. The flea has four different life stages; egg, larva, pupa, and biting adult. The egg is laid, and then hatched as larva. The larva do not eat blood like the adult flea they eat skin cells, flea droppings, dead animals, feces or any other organic matter they can find. The reddish dust that you may see on your pet is the debris from adult fleas; it is the droppings tainted with the blood of your pet (that is why it is reddish in color)
After about two weeks the larva spin a cocoon around themselves using pieces of dirt, debris, and hair as camouflage. If they have access to plenty of food, they will come out of their cocoon in one week after spinning the cocoon. If food is not plentiful they can stay in their cocoon for up to one year. The flea larva and the adult fleas have totally different eating patterns.
Once the adult female flea comes out of her cocoon she must eat before she can reproduce or she will die without ever laying an egg. After she has eaten she can lay up to 20 eggs totaling 500 eggs in her lifetime. This is the reason they are so hard to get rid of!
The adult flea feeds on the blood of their host. The host can be any warm blooded animal including humans. Fleas tend to prefer animals to humans because they like to hide in the fur of the animal. Fleas are equipped with the perfect mouth parts for harvesting the blood of their hosts. They pierce the skin of their host and inject an anti blood clotting saliva. This enables them to feed with ease. A female flea will eat up to 15 times its weight in blood daily, but can go more than 100 days without a meal.