A subclass of dryad. “Hamadryads die with the particular trees with which they are identified” (Hornblower).
Most often, they are associated with oak and poplar trees; however, they are also associated with the Karya (nut bearing trees) and the Ptelea (elms), among others.
The ancient Greeks believed nature to have life and viewed nature as anthropomorphic beings. If a mortal harmed a tree of the Hamadryads, the Gods and dryads punished the mortal severely.
John William Waterhouse. A Hamadryad. 1895