Elm finger 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 finger gall mite is a specialized plant feeder. It can be found on American elm and possibly on other elms.

Elm finger gall mite produces elongated, slender, yellowish-green, finger-like galls on the upper surface of the leaves. The galls are solitary – they do not coalesce into larger galls. They occur singly, mostly along the midrib but also along secondary veins. Sometimes they crowd in the angles between the midrib and the secondary veins.

Tiny, almost microscopic

American elm (Ulmus americana) and possibly other elms

Sources

Common

Order
The superfamily Eriophyoidea (including the family Eriophyidae) was historically classified within the order Trombidiformes, specifically in the suborder Prostigmata. However, molecular phylogenetic analyses have strongly challenged this placement. Current genomic research indicates that eriophyoid mites represent an ancient, basal lineage within Acariformes (now widely recognized as its own distinct order, independent of Parasitiformes). Recent evidence places them as a sister group to the obscure soil mites of the family Nematalycidae. Due to ongoing adjustments regarding their precise evolutionary relationships, placing Eriophyidae directly under the order Acariformes provides a stable and modern taxonomic framework that avoids the unstable suborder debate.