The gall is a smooth, globular or spindle-shaped swelling, usually on a twig or stem and contains larvae or pupae in up to fifty separate chambers.

[2] The gall, does not contain frass, and occasionally occurs on the petiole, midrib,[a] or side veins of a leaf.

The larvae are pale orange or reddish, over-winter in the gall and pupate in the spring.

Correct identification of the host plant is necessary; the similar looking gall on purple willow (S. purpurea) is Rabdophaga degeerii.

This article related to members of the fly infraorder Bibionomorpha is a stub.