Eurois occultus (Linnaeus, 1758)

Host plants:
The larvae are polyphagous on herbs and especially small shrubs such as Vaccinium or Lonicera.

Habitat:
Eurois occultus is particularly typical of cool, bright, montane to subalpine or boreal coniferous forests, which have a well-developed understory of dwarf and other shrubs. But it occurs occasionally also in the hilly stage.

Life cycle:
The caterpillar overwinters. I found a half-grown larva in the Engadine at 2000m above sea level during the day concealed in the moss layer under Lonicera coerulea whose twigs had eroded buds. The caterpillar is fully-grown in May or June, depending on the elevation. The moths fly from late June to August.

Endangerment factors:
Eurois occultus should not be especially vulnerable, even if spruce pole fields (= forest within the meaning of most foresters) are hardly inhabited and if then only under otherwise favourable conditions.

Remarks:
The distribution is Holarctic (temperate Europe, Asia, North America), but in Southern Europe with only a few populations in the mountains.