elm leaf gall mite

Aceria is a genus of tiny mites. They are so small that they are almost impossible to see with the naked eye. Unless a scanning electron microscope is available, a morphological description of an adult individual is useless. However, many mites can be easily identified by the shape of the galls they produce and the plant species on which they are found.

Elm leaf gall mite is a specialized plant feeder. It is found exclusively on American elm. It produces small, variable, globular, yellowish-green, bead-like galls on the upper surface of the leaves. The galls are solitary – they do not coalesce into larger galls. They occur singly between secondary veins. They have a rough surface and may be covered with hairs.

Tiny, almost microscopic

American elm

Sources

7, 29, 30, 82.

Order
The family Eriophyidae was formerly classified within the order Trombidiformes, specifically in the suborder Prostigmata. However, molecular phylogenetic analyses, beginning in the early 2010s, have strongly challenged this placement. Current research indicates that Eriophyidae represents a very ancient and basal lineage within the order Acariformes. While Acariformes was historically treated as a superorder by some classifications, it is now widely recognized as one of the two major orders of mites (along with Parasitiformes). Due to ongoing debates about their precise relationships with other mite groups, Eriophyidae is currently placed directly under Acariformes without being assigned to a specific suborder.