Two resting Damon blue butterflies (Polyommatus damon)

We were exploring a potential site for placing an insect light for attracting nocturnal species in the mountains near Barcelonette, France shortly before dusk. Several diurnal had already settled down for the night, including these two Damon blues.
The prominent dagger-like white streak on the underside of the hindwings (present in both sexes) make this species easy to distinguish from other Lycaenidae. The German common name also alludes to this “dagger” (DE: Weißdolch-Bläuling).