Chute Leech

The Chute Leech is seen in Metroid II: Return of Samus, Super Metroid and as an X Parasite clone in Metroid Fusion, being found on both SR388 and Zebes. It has a flat body and will lie dormant until Samus walks by. Its attack is to jump into the air and then glide down, swaying from side to side using its parachute-like body. Artwork seems to indicate that they have 4 eyes.

An almost identical creature on Zebes, the Choot, has rows of teeth visible on its underside. They are more of a nuisance than a serious threat.

The X Parasite variant glides down much slower and without the swaying effect; on the way down, it will periodically spit globs of acid. It also has noticeably larger fangs.

Manual
"Usually they will lay quietly on the ground or in the liquid. But, when Samus comes close, they will jump up to attack, falling down like a leaf from a tree."