The larva of the gall midge Rhopalomyia baccarum cause galls on Artemisia species such as Mugwort.  The gall affects buds, mainly those near the very base of the stem, which become swollen into a berry-like, fleshy and juicy gall, usually 2 to 6 mm, sometimes slightly larger.  The gall contains a solitary, orange larva. Pupation occurs within the gall.

Gall Adult

When recording the gall please state the host plant and also check the larva, either stating the colour, or if possible, including a photograph of the larva with your record.

Where the host Artemisia species occur.

When the host plants are in leaf, mainly April to September.

True status in Britain is difficult to determine due to problems of identification and lack of records.

Rarely recorded in Leicestershire and Rutland.