Brown Argus (Aricia agestis)
A. agestis is a widespread, warmth-loving species and, as such, is typically found in sheltered areas or on south-facing elevations. It can be found south of a line between Dorset in the west and southeast Yorkshire in the east, along with colonies in Derbyshire, North Devon and Cornwall. It is also found in north and south Wales, but is absent from central Wales. It is not found in Scotland, Ireland or the Isle of Man. Occurring in small, compact colonies, it is not a great wanderer, only travelling a couple of hundred metres, at most, from where it originally emerged. Like its close relative, the Common Blue (Polyommatus icarus), this species will roost communally on grass stems at night. In fact, the two species are sometimes found roosting together.
Two broods are common in central and southern England, with only a partial second brood in north Wales and the north of England. In good seasons, a partial third generation may be recorded in the south. The adults emerge first in central and southern England in early May, peaking at the end of May and the beginning of June, and giving rise to a second brood that emerges at the end of July. In north Wales and northern England, the first emergence starts in early June with any second brood appearing in early August.
Unlike most other members of the Polyommatinae, the ‘blues’, the Brown Argus has no blue scales on its upperside, both sexes being primarily brown in colour as its vernacular name suggests - although the butterfly can exhibit a bluish sheen when at certain angles to the light. Both sexes have beautiful orange spots on the upperside of both forewings and hindwings with the female - illustrated above - being more generously marked. It appears to be doing well in Sussex this season …