Host plants:
The larvae feed on Deschampsia (Avenella) flexuosa, possibly also other grasses.
Habitat:
Stilbia anomala inhabits meagre, at least half shady places in light woodlands, so on embankments where the larval host plant grows. It is found only in atlantic climate influenced areas.
Life cycle:
The caterpillar lives from October to early or mid-April and is still active in winter even at cool temperatures. It then rests openly at straws of clumps. From March, they are mostly concealed in the base of clumps during daytime. The prepupa lies before pupation several months from April to July. The moths will fly in August and September.
Endangerment: strongly endangered
Endangerment factors:
Stilbia anomala is locally threatened by forestry interventions in their narrowly defined habitats. So clearcutting leads to the disappearance of the local population. Additionally eutrophication from the air must be counted among the damaging factors. Overall, the spread is probably also strongly limited by climatic factors.
Remarks:
Stilbia anomala is distributed from the north of Spain across France and England to west Germany (Rhine and adjacent lower moutains). A relic population exists in southwest Norway.