Polyommatus idas (Linnaeus, 1761)

Polyommatus idas: Male [S] Polyommatus idas: Male lower side [S] Polyommatus idas: Female [S] Polyommatus idas: Female lower side [S] Polyommatus idas: Ovum at Genista germanica [N] Polyommatus idas: Larva [S] Polyommatus idas: Larva at Hippophae rhamnoides (Valais, Switzerland) [M] Polyommatus idas: Larva at Helianthemum (Southwestern Alps) [N] Polyommatus idas: Larva at Oxytropis cmpestris (Ticino, Switzerland) [M] Polyommatus idas: Larva (Spanish west Pyrenees, Aisa, 2300m above sea level, early July 2010) [M] Polyommatus idas: Larva with ants (Valais, Täschalpe, June 2010) [N]

Host plants:
The caterpillars feed on Fabaceae, Ericaceae, Cistaceae and Hippophaes rhamnoides. Locally, the species shows a relative restriction to single species. So oviposition takes place exclusively on Sarothamnus scoparia in the northern Upper Rhine Valley, on Hippophaes in the Rhone valley bottom in the Valais (Pfynwald) and in the High Alps preferably on Helianthemum.

Polyommatus idas occurs in extensively managed open country and in broad, sunny forest edges. The butterfly prefers nutrient-poor habitats such as sandy grasslands, pastures and scrubby, dry places.

Life cycle:
The egg hibernates and is therefore usually deposited at woody parts. Adapting to such structures may be one reason for the regional preference of single host plants. So I found a lot of eggs in the north Bavarian Steigerwald on woody Genista germanica or on the Swiss Täschalpe on shoots and moss in Helianthemum pads.
At higher elevations, the adults fly in a single generation between late June and mid-August. At lower elevations, there are mostly two generations, rarely even a partial third.

Endangerment: endangered

Endangerment factors:
In the lowlands Polyommatus idas is threatened by extinction due to the loss of suitable semi-open structures (large forest edges with brooms, sandy grasslands etc.). In the (central and southern) Alps Polyommatus idas is still at little risk up to 2500m msl.

In Europe, Polyommatus idas occurs locally from the Iberian Peninsula to Northern Scandinavia (misses in the British Isles). In southern Europe the distribution is more restricted to the mountains and Polyommatus idas misses mostly in the very south and on the most Isles. Additionally, Polyommatus idas is found in parts of more northern Asia.

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