Hematophagy

Since blood is a fluid tissue rich in nutritious proteins and lipids that can be taken without great effort, hematophagy is a preferred form of feeding for many small animals, such as worms and arthropods.

Some intestinal nematodes, such as Ancylostomatids, feed on blood extracted from the capillaries of the gut, and about 75 percent of all species of leeches (e.g., Hirudo medicinalis) are hematophagous.

[2][3][4][5] Several complementary biological adaptations for locating the hosts (usually in the dark, as most hematophagous species are nocturnal and silent to avoid detection) have also evolved, such as special physical or chemical detectors for sweat components, CO2, heat, light, movement, etc.

Insects and arachnids of medical importance for being hematophagous, at least in some species, include the sandfly, blackfly, tsetse fly, bedbug, assassin bug, mosquito, tick, louse, mite, midge, and flea.

[citation needed] The anticoagulants in the laboratory-raised leeches' saliva keeps fresh blood flowing to the site of an injury, actually preventing infection and increasing chances of full recovery.

In a recent study a genetically engineered drug called desmoteplase based on the saliva of Desmodus rotundus (a vampire bat) was shown to improve recovery in stroke patients.

Some societies, such as the Moche, had ritual hematophagy, as well as the Scythians, a nomadic people of Eastern Europe, who drank the blood of the first enemy they killed in battle.

Sucking or licking one's own blood from a wound to clean it is also a common human behavior[dubious – discuss], and in small enough quantities is not considered taboo.