The leech appears in Proverbs 30:15 as a symbol of insatiable craving. The creature is notorious for its persistent blood-sucking, never satisfied until gorged. The proverb uses it to introduce a numerical saying about things that never say 'enough'—Sheol, the barren womb, thirsty earth, and fire. Some ancient interpreters suggested this might refer to a vampire-like demon or even represent the name of a sage, but the literal understanding as a leech fits perfectly with wisdom literature's use of natural observation for moral instruction. The image powerfully captures relentless, parasitic desire.