Acalitus stenaspis is an eriophyid mite which causes galls on beech (Fagus species).

In spring leaves may be stunted, thickly covered in silver-grey hairs, and may be folded with wavy veins and contain mites.

[2] The gall most associated with this species is the edge of the leaf curling upwards and forming a very tight roll, which is often overlooked.

During the summer, numerous mites live inside the gall feeding on a mass of tiny hairs.

[5] Arthrocnodax gemmarum is an Inquiline which lives in the gall alongside the gall-causer, [6] Found in Europe, including Bosnia and Herzegovina, Croatia, Czech Republic, Denmark, France, Germany, Great Britain, Ireland, Italy, Kosovo, Latvia, Lithuania, Montenegro, North Macedonia, Poland, Serbia, Spain and Switzerland.