Euura collactanea

The gall is found on the underside of a leaf of the host plant. It is globular and up to 5 mm in diameter. Descriptions vary according to the source. According to the Plant Parasites of Europe website, the gall can be hairy and sometimes warty. The colour varies from bright red to a red-tinged green. Redfern et al. (2011) describe the gall as having brown warts and either no hairs or slightly hairy. The galls can be found on the leaves of creeping willow (Salix repens) and rosemary-leaved willow (Salix rosmarinifolia).^[1][2]

The gall is found, in the west from Great Britain and Ireland (locally common), north to Sweden and east to Lake Ladoga, Russia.^[3][2]