Hematophagy (sometimes spelled haematophagy) is the habit of certain animals of feeding on blood (from the Greek words, haima, blood, and phagein, eat). Since blood is a fluid tissue rich in nutritious proteins and lipids and can be taken without enormous effort, hematophagy has evolved as a preferred form of feeding in many small animals, such as worms and arthropods. Some intestinal nematodes, such as the Ascaris, feed on blood extracted from the capillaries of the gut and about 75% of all species of leeches (e.g.