Wingspan c. 11-15mm.
Distributed locally in scattered localities over England and south Wales, C. servillana frequents damp woodland margins and hedgerows where the foodplants, goat willow (Salix caprea and grey willow (S. cinerea grow.
The larva feeds internally in a slender twig of sallow, causing a slight swelling or gall, which can be difficult to find. The twigs chosen are generally one or two years old. As the moth emerges, the pupal exuviae protrudes from the exit hole making vacated galls easier to detect.
The adults fly in June and July, from afternoon into the evening.