Class Arachnida (Arachnids)
Subclass Acari (Mites & ticks)
Order Trombidiformes (Trombid mites)
Family Eriophyidae (Gall mites)
Species Aceria nalepai (Fockeu, 1890)
Gall height 3 mm.
A mite which causes pouch galls to form on the leaves of Common Alder (Alnus glutinosa), in the angles between the midrib and the primary veins. They appear either alternately or in pairs and may run from the petiole to within two or three veins of the leaf apex. The galls are filled with russet hairs amongst which the mites live, and these hairs often project through to the underside of the leaf.
Seen spring and summer, and found wherever the host tree grows. A native speices, common and widespread.
Found in local wood, South Staffordshire October 2020. © Peter Hillman.