Two butterflies on a grass stalk. Blue one with wings open.

Silver-studded Blue. Photo: Brian Arnold

A lovely small butterfly which is not very mobile: individuals will only fly a maximum of 50 metres, so colonies tend to be static and well-defined. The adult butterflies only live 4-5 days. Declining nationally, but doing quite well in Dorset.

This species relies very heavily on two species of black ant. The female butterfly lays her eggs close to a black ants' nest and, when the little caterpillars hatch, the ants carry them inside the nest and ‘farm’ them by ‘milking’ them for sugars and amino acids, escorting them outside at dusk to feed, allowing them to pupate in the passages of the nest and accompanying the emerging butterflies up to the surface.

Where to see

Habitat: Found in two types of habitat: mainly heathland, but also limestone (or occasionally chalk) grassland.

Caterpillar foodplants: On Heathland: Ling, Heathers, Gorse. Both particuarly on the edge of clear ground. On limestone: Bird's-foot Trefoil; Common Rock Rose.

Best places: Found only in the south and east of Dorset.
Heathland colonies: Higher Hyde, Studland, Tadnoll, Avon Heath Country Park, Sopley Common*, Slop Bog, Ferry Road West*.
Limestone colonies: Portland Broadcroft, Portland Tout,
*Indicates particularly high numbers

Reported from the following locations last year*:

When to see

A single-brooded butterfly, peaking in July.

Sightings by month (last 5 years)*:

Sightings this year*:


Notes

Size: small.

The Silver-studded is the blue butterfly with the strongest relationship with ants. Like some other blues, this is true in both the caterpillar and the chrysalis stages, but with the Silver-studded it applies to the adult stage too: the females look to lay their eggs not just on the best foodplants, but also near nests of the ants which attend them. The ants actually find the newly-hatched caterpillars and take them into their nests.

Our second smallest blue butterfly: only the Small Blue is less big. It can be very variable in its markings.

The male upper wings are deep blue with a black outer band and a white fringe, though this can be very narrow or worn off in old age. The black band is wider than on the Common, Holly or Adonis Blue males.

The female upper wings are dark brown also with a variable white fringe and rather sketchy orange markings on the outer edges of the upperside forewing, though clearer ones on the edges of the hindwing.

The most definitive point to look for is on the hind underwing, where there should be a small silver stud within the black mark, which itself is between the orange and white marks towards the edge of the wing – more easily seen in a photograph than explained. This may sometimes be almost absent and is quite hard to see while the butterfly is on the wing, so get some photos and enlarge them later.

Its flight is ground-hugging, slow and fluttery – if it flies strongly away over the hedge, it is not likely to be a SSB!

The female is most easily confused with the Brown Argus, which is the same size, and neither species has a mark on the underside of the upperwing nearer the body than halfway.

Photo gallery

Click thumbnails to view larger images.

*Please note: The charts shown on this page are drawn only from casual sightings submitted to this website. Records from this website will be added to a lot more data collected throughout the year and used to compile the five-yearly Butterfly Atlases for Dorset and the UK.