Beech leaf gall midge, Heeswijk-Dinther, Netherlands

As the name suggests, this gal is found on leafs of beech trees, typically on the upper-side. The gall is about 1cm in size. The midge causing it is one of the largest gall midges in Europe, at 4mm. The gall changes in color as it ages, from green to red.

As the leaf dries up in autumn, the gall drops to the forest floor, where the larva inside overwinters. In spring, the adults emerge and lay eggs on the buds of beech tree leafs.