Hadena clara (Staudinger, 1901)

Host plants:
The caterpillar lives on Silene species that grow directly on rocks (usually steep cliffs). In the Southwestern Alps, I found it on Silene cordifolia. Additionally, Silene vallesia is likely to be important in the Alps, with which distribution from the Maritime Alps to the Valais (Saas Fee) the spread of the moth correlates. In Greece, I recorded larva on Silene saxifraga.

Habitat:
Hadena clara inhabits steep rocky slopes which are mostly overgown with lichens. Important is the presence of a suitable Silene species (in the Alps Silene cordifolia and most likely Silene vallesia, in Greece Silene saxifraga).

Life cycle:
The pupa hibernates. The moths fly mainly in July and August, sometimes starting already in the end of June. I found the eggs and young caterpillars in mid-August 2010 (rather late mountain year) and in mid-July 2011 (early mountain year) in 2200 to 2500m above sea level in the south-western Alps (border ridge Italy-France) on steep rocks at Silene cordifolia.

The older caterpillars (especially the last two instars) are very colourful and so well camouflaged on lichen-rich rocks during the day when resting in crevices or at the base of the host plant.

Remarks:
Hadena clara occurs in the north African, European and Asian high mountains. In Europe it occurs for example in the Sierra Nevada (Southern Spain), the Southwestern Alps and the Balkan peninsula. Most populations are found above 1700m above sea level, rarely deeper. The upper limit is likely to be at 2800m above sea level in the Alps.

In the Alps, the distribution correlates strikingly with the probably most important host plant Silene vallesia, which is limited to the Southwestern Alps as the moth and reaches in the northeast the Valais. Silene cordifolia is endemic to the Southwestern Alps (Maritime Alps) and is absent further north. But this species is likely the cause for the commonness of Hadena clara in the Maritime Alps. Both Silene are found on acidic substrate only. Thus Hadena clara is likely to be missing in pure limestone areas at least in the Alps, but occurs there in the Balkans (Greece).