Nationally scarce (Nb) on sea cliffs and rocky hillsides, along the coasts of southern and western Britain. Resident on chalk cliffs on the south side of the Isle of Wight, around Freshwater, St Catherine's Point and the Ventnor area. There is a single record from the New Forest in 2006, which requires validation. Wingspan 35-40 mm. The most likely confusion species is
White-line Dart E. tritici, but in Square-spot Dart the region beyond the postmedian line is almost without markings and nearly always lacks any trace of the wedge-shaped marks which are so often a feature of White-line Dart (MBGBI Vol 9), however some individuals can be separated only by dissection of the genitalia. Larva feeds on herbaceous plants such as Common Rock-rose and Lady's Bedstraw, over-wintering as an egg or small larva.