Gall diameter 8 mm. A tiny Cecid fly called Dasineura urticae causes these swellings to form on Stinging Nettles (Urtica dioica).
The eggs are laid at the base of the leaf or in a leaf vein. The hatching white larva then forms a pouch, which can range from green to purple, in which it feeds on the plant tissue.
Found wherever the host plant Urtica dioica grows. Common and widespread throughout Britain.
Class Insecta (Insects)
Order Diptera (True Flies)
Family Cecidomyiidae (Gall Midges)
Species Dasineura urticae (Perris, 1840)
Photos: Local riverbank, South Staffordshire. July 2020 © Peter Hillman