Silver-studded blue

The silver-studded blue (Plebejus argus) is a butterfly in the family Lycaenidae. It has bright blue wings rimmed in black with white edges and silver spots on its hindwings, lending it its name. P. argus can be found across Europe and east across the Palearctic, but it is most often studied in the United Kingdom where the species has experienced a severe decline in population due to habitat loss and fragmentation.

The butterfly is adaptable to different habitats and is found in heathland, mossland, and calcareous grassland.

The caterpillar larva is very variable, usually light green with dark dorsal spots, sometimes grey or dark brown with pale spots. In early summer and autumn the larva feeds on plants such as Coronilla, Trifolium, Colutea, and Genista. The larva and pupa are associated with the ant Formica cinerea and live in its nests. The pupa is elongate, green with red dorsal line; abdomen above yellowish green. There are two broods in the south, with adults on the wing in May and again from July onwards, but there is only one brood in the north. They favour sandy soil, like the ant.

Geographic range

P. argus is found across the Palearctic.

Heathlands are able to meet the needs of P. argus due to burning, cutting, and other disruptions of mature heaths. When the weather is warm, sunny, and the breeze is still, P. argus spends less time in shrub dense habitats and more time in flight and finding host plants in areas rich in calcareous heath. These areas tend to be on exposed hillsides. For this reason, it often appears that the habitat of P. argus shifts with weather conditions.

Home range and territoriality

Adult P. argus tend to be very sedentary, only moving around every day. For this reason, the butterflies colonize on discrete territory and patches of land. Some butterflies, though, disperse and move over a kilometer between colonies. This is rare, however, as these butterflies tend to form metapopulations.

Adult diet

Adults feed on nectar. In mosslands, the butterflies tend to lay their eggs on the underside of the fronds of the Bracken Fern. This fern appears to be preferential for oviposition because they attract ants. In limestone grasslands, P. argus lays eggs at the stem of Lotus corniculatus and at the base of Helianthemum chamaecistus.

Adult

P. argus adults emerge in the end of June and beginning of July and engage in flight into the beginning of August.

Subspecies

P. a. argus Scandinavia
P. a. aegon (Denis & Schiffermüller, 1775) Karelia
P. a. cleomenes (Fruhstorfer, 1910) Carpathians
P. a. wolgensis (Forster, 1936) southern Europe, Kazakhstan, Tian-Shan, Tarbagatai, Saur, southern Altai
P. a. bellus (Herrich-Schäffer, 1844) Asia Minor, Kurdistan, Levant, Caucasus, Armenia, Talysh
P. a. obensis (Forster, 1936) Ural, western Siberia
P. a. clarasiaticus (Verity, 1931) eastern Altai, Sayan, Transbbaikalia, western Amur
P. a. pamirus (Forster, 1936) Pamirs-Alai, Tian-Shan
P. a. coreanus Tutt, 1909 eastern Amur, Ussuri, Korea
P. a. micrargus (Butler, 1878) Japan, Sakhalin
P. a. asur Agenjo, 1966 Villasur, Spain
P. a. bejarensis (Chapman, 1902) Castilla-Leon, Béjar, Spain
P. a. branuelasensis (Tutt, 1909) Branuelas, Spain
P. a. casaiacus Chapman, 1907 Casayo, north-western Spain
P. a. claraobscura (Verity, 1931) Larche, Basses-Alpes, 1700-2000m, France
P. a. seoki Shirozu & Sibitani, 1943 Saishuto, Korea
P. a. vigensis Tutt, 1909 Vigo, north-western Spain
P. a. sultana (Forster, 1936) Asia Minor

Mating

When a male detects a female sitting quiescently, he flies towards the female. As he approaches the female, he flutters his wings in broad sweeping movements and she raises her abdomen while vibrating her half-open wings in a mate refusal posture. The female then flies away and is followed by the male. Once she lands, the male flutters around, either in the air before descending or after landing. Additionally, the percentage of heathland has decreased by over fifty percent in the United Kingdom, greatly affecting the butterflies for which this was a primary habitat.