Leech. A leech may be described as a type of worm with suckers at each end of its body. One end also contains a mouth. Some species of this animal even have tiny teeth. Parasitic leeches attach themselves to a person or an animal, from which it sucks blood for nourishment. A leech of this type secretes chemicals which keep the blood flowing freely.
In primitive times, physicians used leeches to “bleed” a patient and purge his body of what was thought to be contaminated blood. But an untended leech could cause pain and damage. In his Proverbs, Solomon may have had the blood-sucking nature of this animal in mind when he spoke of the leech’s “two daughters” who cry “Give! Give!” (Prov. 30:15).
Source: [Anon-Animals]