Silver-studded Blue (Plebeius argus)
Male. Taken at Gracac, Croatia, on June 7th 2017.
(1/640th sec at f14. Approx 3x lifesize)
Male underside. Taken at Trigrad Gorge, Bulgaria, on June 23rd 2014.
(1/400th sec at f9. Approx 3x lifesize)
Female. Taken at Silchester Common, Hants, on July 16th 2016.
(1/125th sec at f14. Approx 3x lifesize)
© David Hastings
DescriptionWing span: 26 - 32 mm
There are two subspecies found in Britain. argus occurs throughout its range. caernensis is restricted to the Great Orme in North Wales. This subspecies can be distinguished by its smaller size, and the amount of blue in the female.
The strongholds of this butterfly are the heathlands of southern England and East Anglia. There are colonies on the coasts of North Wales, Suffolk, Norfolk and Cornwall.
This species is typically found on heathland that has not become too overgrown. It is also found on both limestone and chalk grassland and was formerly found in upland mosses. This species is a warmth-loving butterfly and is often found in sheltered areas, or those that are south-facing. It is found in close-knit colonies, with individuals rarely flying any distance. Most colonies contain fewer than a thousand adults.
Adults typically fly in July and August, although many colonies, including those in the east of England and north Wales, emerge in the middle of June. There is one brood each year. The over-wintering stage is the ovum, with the larva fully formed inside. Newly-emerged adults, larvae and pupae are often attended by ants (especially the black ant Lasius niger), which offer them some protection from predators.
The primary larval foodplants are Bell Heather (Erica cinerea), Bird's-foot Trefoil (Lotus corniculatus), Common Rock-rose (Helianthemum nummularium), Cross-leaved Heath (Erica tetralix), Gorse (Ulex europeaus), Heather (Calluna vulgaris) and Horseshoe Vetch (Hippocrepis comosa). Adults feed primarily on Heather.
This butterfly has a rather slow, fluttering flight, often close to the ground. At night, adults gather in communal roosts, often on tussocks of grass.
This species is listed as Vulnerable in the latest Red List of British Butterflies (PDF).