Dryad

Physiology
The wall widow usually takes the form of a decrepit elderly woman made of gnarled bark and protrudes itself from the tree or wall it possesses to attack when any living thing got too close to it.

Once in Super Castlevania IV, the Wall Widow took the form of a mud covered young woman in what appears to be a dress as opposed to its elderly form in its other game appearances.

Game Appearances
Haunted Castle

Super Castlevania IV

Castlevania X68000

Castlevania Chronicles

Locations
Normally found in trees and sometimes walls and is usually a rare enemy. Here are the locations in which the Wall Widow is found in the above games:

Haunted Castle-

Stage 1: Graveyard: Appears from a tree in the latter half of the level.

Super Castlevania IV-

Stage 4: Tower of Death: Appears from a wall at the top of the staircase from the wall on the right.

Castlevania X68000 and Castlevania Chronicles-

Stage 3: Found in various trees in the first section of this level.

(Will be added to as more are found)