Euura

Euura is a genus of sawflies of the family Tenthredinidae, subfamily Nematinae. Some of the larvae feed externally on plants and some form plant galls on willows (Salix species). In the case of the gall-forming species, when the female lays her eggs she injects a stimulant and the gall starts to form before the eggs hatch. Most sawfly galls are hard and individual larva tend to inhabit the gall, feeding on the tissue and leave the gall to pupate in the soil. Most of the species are monophages (i.e., specific to one species of willow) although the type species, Euura mucronata, is polyphagous feeding on over thirty species of willow.

Most groups of insects tend to have maximum numbers of species in the tropics and decrease towards the poles. The Nematinae reverse this trend with the highest number probably occurring in the boreal forest zone. The reason is not fully understood but could be because of the abundance of species of willow in the region. In the Western Palaearctic all of the species of Euura are attached to Salix species as hosts for their larva. Reports of European species of stem-galling Euura, galling poplar (Populus species) remain unconfirmed, although at least five species in North America do gall poplars.