This is the highest of the European brassy ringlets, flying very locally in Switzerland, Austria and Italy, typically above about 2300m. I have found it just below the snowline, on a slope with short grass and rocky outcrops.

In appearance, this species is somewhere between common brassy ringlet and Swiss brassy ringlet. The apical spots on the forewing are quite well developed but usually just separated by the grey ground colour along the vein (in common brassy ringlet the black spots often, but not always, touch each other) but the spots on the hindwing are present but weak (usually strong in common brassy ringlet and usually weaker still in Swiss brassy ringlet). The orange of the forewing reaches in towards the cell with two 'fingers', clearly visible in the first picture here. The underside is a particularly lustrous bluish silver. None of these characters is distinctive alone and I have seen individuals of common brassy ringlet that I would have identified as de Lesse's brassy ringlet if I had seen them in the right place. Confirmation of populations is sadly only possible by taking specimens - something I do not do.

The larval foodplant is Festuca quadriflora. Caterpillars hibernate twice, so the full development takes two seasonal cycles, and the adults fly in a single generation in July and August.