Host plants:
The larvae feed on Asteraceae, especially species like Achillea millefolium or Artemisia sp. I found the young larva on Artemisia camphorata (=A. alba) in the French Alps in autumn.
Habitat:
Thetidia smaragdaria mostly inhabits dry and warm, but also humid and warm habitats like nutrient-poor grasslands, embankments, coastal areas and steppe slopes.
Life cycle:
The larva hibernates and is mature in April or May. The adults occur in one or two (depending on locality) generations between May and September, most often with peak in June or July.
The larva camouflages by webbing dry plant parts on its body which leads to a bizarre and hardly recognizable appearence. Furthermore its movements are slow and staggering.
Endangerment factors:
Thetidia smaragdaria is threatened especially in the north because of the massive loss of open, extensively managed and dry-warm habitats.
Remarks:
Thetidia smaragdaria is found from Spain and SE-England (here only very local at the coast) across Southern and Central Europe and parts of Asia to Japan.