The larva feeds on Astragalus species such as Astragalus monspessulanus and A. sempervirens.
Polyommatus escheri colonizes sunny, hot and dry slopes to about 2000m asl in the Alps. It often occurs also in very sparse mountain forests (pine, larch) such as the larch forest beneath the Täschalpe in Valais.
The adults fly mainly in a single generation in July and at lower altitudes already from June. The caterpillar overwinters. I found mature larvae on Astragalus monspessulanus in the Maritime Alps near Cuneo in late May on a hillside where Pyrgus bellieri flies. In mid-July I observed there many adults feeding especially on lavender.
In Valais (Täschalpe, 2000m asl), I found several half-grown to quite mature caterpillars in June 2010 and in the Provence at about 1000m above sea level in late April 2010.
In southern Europe Polyommatus escheri is not at greater risk. In Valais, however, it has already lost many habitats (viticulture, tourism, roads etc.).
Polyommatus escheri occurs in Northwest Africa (here locally) and Southern Europe (Balkan Peninsula, Spain, Southern France, parts of northwest and Central Italy). To the north, Polyommatus escheri occurs in the Southern Alps (to the east about to Lake Garda), the Valais and the Rhine Valley near Chur in Switzerland.