Aceria mackiei, commonly known as the maple spider mite, is a tiny arachnid belonging to the family Eriophyidae. These mites are specialized pests that primarily infest maple trees, causing damage to the leaves. They are less than 0.2 mm in size and have a reddish-brown color. Aceria mackiei feeds on the sap of the leaves, leading to discoloration, curling, and distortion of the foliage, which can negatively impact the overall health of the tree.