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 lower altitudes. In the northern foreland of the Alps it is often common on and around bogs in spruce forest or grassy edges.

Life cycle:
The caterpillar overwinters. In spring, it sometimes rests on the still quite nude twigs of Vaccinium during daytime. 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 which twigs had eroded buds. The caterpillar is fully-grown in May or June, depending on the altitude. The moths fly from late June to August. In autumn (especially September to early November) the young larvae are easily nbeaten from the herb layer or from dwarf shrubs.

Endangerment factors:
Eurois occultus should not be especially vulnerable especially in the mountains, even if intense spruce plantations are hardly inhabited.

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