''Aculus tetanothrix'' is a

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

mite Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear evid ...

which causes

gall Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external Tissue (biology), tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissu ...

s on the leaves of

willow Willows, also called sallows and osiers, from the genus ''Salix'', comprise around 400 speciesMabberley, D.J. 1997. The Plant Book, Cambridge University Press #2: Cambridge. of typically deciduous trees and shrubs, found primarily on moist ...

s (''Salix'' species). It was first described by

Alfred Nalepa Alfred Nalepa (19 December 1856, in Werschetz – 11 December 1929, in Baden bei Wien) was an Austrian zoologist specializing in the field of acarology. He studied natural sciences at the University of Vienna, and from 1886 was associated with th ...

in 1889.

Description of the gall

The gall is a green or reddish, rounded pouch or pustule on the upperside of a leaf, which also protrudes on the lower surface of the leaf. There is a slit-like opening on the underside of the leaf which, when mature, is hairy inside but the hairs do not protrude outside of the gall. Many mites can be seen within the opening. The galls are found on white willow ( ''S. alba''), eared willow ( ''S. aurita''), grey willow ( ''S. cinerea''), ''S. eriocephala'', crack willow ( ''S. fragilis''), ''S. integra, bay willow ( ''S. pentandra''), purple willow ( ''S. purpurea''), Sitka willow ( ''S. sitchensis''), ''S. smithiana'', almond willow ( ''S. triandra'') and common ossier ( ''S. viminalis''). ;Similar species It is possible that ''A. tetanothrix'' is one of a number of closely related species, and the galls on ''S. alba'' could be caused by ''A. salicisalbae''.

Distribution

''Aculus tetanothrix'' has been recorded from Germany, Slovenia, Great Britain (England, Scotland and Wales), the Netherlands, Norway, Russia, Sweden and the USA.

Reference

External links

iNaturalist
{{Taxonbar, from=Q15694204 Eriophyidae Arachnids of Europe Arachnids of North America Animals described in 1889 Taxa named by Alfred Nalepa Willow galls