Last modified: April 5, 2021, 12:17 p.m.
Wingspan is about 10 mm.
A white, somewhat sticky cocoon, the channel to the exit hole is lined with white silk. Pupa shining pale brown.
The larva lives inside the stem causing a spindle-shaped gall, up to 15 mm long and 4 mm broad, mainly in the top- and side-stalks, preferably in a flowering side-stalk.
Before pupation an exit hole is made in the lower part of the gall, leaving only a thin layer of bark. The pupa lies with its head downwards in the cocoon.
The species hibernates in the adult stage.
One generation a year: from mid-July till mid-September, and after hiberation till the end of May.
Monophagous on Epilobium hirsutum.
Mainly in damp situations like marshes, roadside ditches, but also in drier habitats.