The larva of the gall midge Dasineura fraxinea causes galls to form on Ash (Fraxinus).  The galls are in the leaf blade, 3 to 8 mm diameter with an irregular opening at the underside; often several in a leaflet. Larva solitary, white. 

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Where Ash is present.

Galls may be found when Ash is in leaf.

Univoltine, hibernation in the soil.

Fairly widespread in Britain.

Status in Leicestershire and Rutland not known.