Aceria brachytarsus

Aceria brachytarsus, formerly Eriophyes brachytarsus, also known as the pouch gall mite or the walnut purse gall mite, is an eriophyoid mite that produces leaf-pouch galls on various species of walnut trees including Juglans californica. The gall produced by this mite initially looks like a bladder gall. This gall has been observed in California, Iran, and Spain.