Aricia nicias
Hostplant: Geranium sylvaticum, possibly also G.sanguineum.
Lifecycle and behavior: Female laid eggs usually on the underside of leaves. Most sources say that this species hibernates as egg in Scandinavia and as larva further south in Europe. In my breeding however, most of the eggs hatched after 10-13 days and the larva went all the way to imago in the same year, hatching in the middle of october! This is most certainly abnormal behavior. The whole larval stage lasted about 4 weeks. Pupation stage lasted 10-12 days. The adult butterfly has its main flight period in July and August.