Polyommatus argus (Linnaeus, 1758)

Host plants:
The caterpillar feeds on Fabaceae, Ericaceae (e.g. Calluna) and Cistaceae (e.g. Helianthemum). On the Swabian Alb it lives mostly on the Fabaceae Lotus, Coronilla and Hippocrepis.
Locally, also other plants may be relevant. In Romania, I observed larvae on Limonium (Plumbaginaceae).

Habitat:
Polyommatus argus can reproduce in various habitat types such as hot calcareous grasslands, quarries, acidic heathlands, moors and clearcuttings.

Life cycle:
The adults fly in a single generation in June and July (on bogst sometimes still in August). Only in warm and low regions (e.g. the Upper Rhine) or in the south there are also two generations from May to early September. The caterpillar overwinters in the egg shell and is mature in the end of May or in early June. It is often accompanied by ants. During the day, it can sometimes be found under the plants on the earth in the moss and litter or in ant nests below the host plants.

Endangerment: regionally endangered or decreasing

Endangerment factors:
Polyommatus argus is threatened by eutrophication and intensification of the habitats, succession (overgrowth) and direct habitat destruction, but still occurs at the moment at many sites thanks to its not very special requirements.

Remarks:
The distribution extends across large areas of the Palearctic (Europe and temperate Asia to Japan).