Last modified: Jan. 20, 2020, 1:10 p.m.
A widespread but not very common species throughout Belgium.
Head dark brown; forewing ground colour golden brown; white pattern consisting of a straight basal streak, a patch on the dorsum near the base, four costal and three dorsal striae, the first costal is characteristis with its rectangular shape; a patch of black scales in the apical area.
An elongated, tentiform mine on the underside of a leaf, sometimes reaching from the main vein till the leaf margin, situated between two secondary veins. The last instar applies so much silk in the mine that it is sometimes contorted into a tube. The frass is concentrated in a corner of the mine. Many times there are several mines on one leaf.
See also gracillariidae.net and bladmineerders.be.
A white cocoon without applying frass.
The species hibernates in the pupal stage, inside the cocoon between fallen leaves among leaf litter on the ground. After emergence of the adult, the pupal skin protrudes through the mine.
Two generations a year: from mid April till the end of May and in July–August.
The species is monophagous on Alnus incana, but it has also been recorded from Alnus glutinosa in Belgium.