There is some doubt about the early records as this and the following species were lumped together until about the middle 1920's. Roughly speaking, they can be separated on time of appearance and the position of the discal spot on the forewings vis a vis the two cross-lines (see Skinner, p. 28). S. mucronata usually appears from the last week in May throughout June, but there is a certain amount of overlap between this and S. Iuridata which is on the wing from late June throughout July, as its trivial name would indicate. Heathy habitats where gorse and broom flourish (their foodplants) are the places to be searched for both. The present species is much less common than its relative. We have records from Waldridge Fell, Teesdale, Chopwell, Hamsterley Forest, Sacriston, etc. [...].