This species is found commonly, in some years abundantly, in all grassy areas from moorland and upland pasture to coastal heaths and mature sand dunes [...] Females are occasionally met with in which the basal streak expands to occupy most of the forewings [...] The depradations that this species can at times cause to upland grassland and heather are too well known to require further comment here, save to say that the population explosions that give rise to this phenomenon seem to be happening less frequently than they used to. Such an explosion occurred on a part of Pikestone Fell, just beyond St. John's in 1981, when about 14 acres of Calluna vulgaris were so badly eaten that the area appeared black from a distance: it took nearly three years to recover. [...] The moth is on the wing from the second week in July to the end of August, averaging up to a fortnight later at altitude.