Host plants:
The caterpillar lives primarily on dying and dead leaves, especially oak, but also of ash, etc.
Habitat:
Herminia grisealis inhabits light deciduous forests. I found caterpillars in July 2011 (Alb) by tapping about 10 to 15 years old oaks, which showed a high proportion of dying, mildew-damaged leaves and additionally on branches that were broken about 6 to 8 weeks ago and now were lying on the ground, still leafy. Such obviously more nutrient-rich food sources are preferred by Herminia grisealis, but also other Herminia species, Paracolax, Trisateles or Polypogon against old fall foliage on the soil. In September 2012, I tapped larvae from Clematis vitalba (many dead leaves of other species) in the Upper Rhine Valley.
Life cycle:
The pupa overwinters. The moths fly in one or two generations from May to September. In the warm year 2011 a second generation was observed also on the eastern Swabian Alb.
Remarks:
You can easily find the caterpillars, together with other related species, by tapping broken branches that are already lying around for a few weeks and still bear the leaves.
Herminia grisealis is widespread in Europe and is also found in temperate Asia to Japan.