The species develops on oak (Quercus robur, Q. pubescens and Q. petraea), only on young bushes. In southern Europe eggs are deposited also on other oak species such as Quercus coccifera.
Satyrium ilicis colonizes clear, warm woods, coppice forests, clearings and clearcuttings, forest edges, windthrow areas or grove rich slopes. In the south, it also occurs in the Mediterranean maquis, light downy oak bushland and Quercus coccifera scrub.
The egg respectively the developed larva within the egg shell hibernates. The larva hatches in late March or in April and lives in the sprouting buds and later on fresh leaves. Mature larvae are observed from mid-May to early June, the butterflies then between June and late July, more rarely still in early August.
The caterpillar lives mostly on small oak bushes below 1-2m, usually around 0.5m in height. Oviposition takes place usually very close to the ground in a few centimeters above ground on stems of young saplings and only significantly rarer on higher parts. Satyrium ilicis is easy and all year detectable by searching for eggs, since the eggs stay visible also after the hatching of the caterpillars.
Endangerment: threatened with extinction
North of the Alps, Satyrium ilicis is highly endangered due to changes in forest structure. The reasons are dark forest management, abandonment of traditional forest management (grazing in the woods, coppicing) as well as the eutrophication and uniformization of the landscape. Moreover, the supposedly natural silviculture with its claim for avoiding clearcuttings and preferring single-tree selection instead has an disastrous impact on the light forest fauna and flora which is dependent on sunny inland forest sites. Formerly (before humans) flooding dynamics, beaver and large herbivores (wild cattle, etc.) provided favorable structures. In earlier centuries, man took over habitat management by above mentioned uses. But today the clean Central European forest is dominated by often boring, uniform and more species-poor, dark high forests!
In southern Europe Satyrium ilicis is threatened much less. For example in Northern Greece, the butterfly is often one of the most common species in July (own observations in Olympus, Falakron, Prespa Lakes regions).
In Central Europe Satyrium ilicis is still present almost exclusively in outdoor museums of traditional forest management as parts of Franconia (Steigerwald). In the 90s, the hurricanes and their windfall areas offered places with better conditions, but now these have become overgrown again and any new storms come soon too late. This can not be belied by individual new records due to increased observation activity as on the eastern Swabian Alb, where I was able to detect Satyrium ilicis at about a dozen new sites since 2007).
The total distribution covers Central and Southern Europe to Western Asia (e.g. Asia Minor). In Europe, the northern boundary is in the southern tip of Sweden. In the south, the butterfly misses on some Mediterranean islands such as Corsica, Sardinia or Crete (but present in Sicily).