Eriophyes inangulis is a mite that forms the alder vein angle gall.[1] It develops in a chemically induced gall; a sub-spherical distortion rising up from the upper surface of the leaves of alder trees Alnus glutinosa along the midrib. Synonyms are Eriophyes laevis inangulis, Phytoptus laevis, and Cephaloneon pustulatum.[1]
The gall's appearance on the upper surface is sub-spherical, smooth and may vary in colour from pale yellow-green to deep red. The adult mite lives on alder tree sap, sucked from the cell tissues. The galls cluster along the midrib in the angle of the veins.[2] The wide opening and interior on the lower epidermis and is lined with large numbers of small hairs. Galls may be so numerous that the leaf expansion is inhibited.[1] [3]
The galls induced appear not to affect the health of trees infected with these mite species and no practical way of controlling or preventing them exists.[4]