Host plants:
The larvae are polyphagous, but seem to occur often on Silene nutans and other pinks when young. I found eggs in a graden meadow on Rumex obtusifolius in Schwäbisch Gmünd (Germany, 2012).
Habitat:
Hada plebeja inhabits nutrient-poor dry grasslands, meadows, wetlands and is also found in residential areas. In the Alps, it rises to at least 2400m above sea level (e.g. larval observation in Engadine).
Life cycle:
The pupa hibernates. Adults are found from mid-May to July and occasionally in a very partial second generation even later. I obtained caterpillars several times from flowers of Silene nutans (Swabian Alb, June 2007), so that oviposition and juvenile development seems to take place often on Caryophyllaceae (but not exclusively). The older caterpillars live very concealed on the ground and move on to other plants (like Asteraceae).
Remarks:
Hada plebeja is widespread in Europe and extends to Central Asia and Mongolia.