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Silver-studded Blue

Plebejus argus

  • Family: Gossamer-winged Butterflies – Lycaenidae
  • Subfamily: Blues – Polyommatinae
  • Wing span: Very small, 22–27 mm (0.86–1.05 in.).
  • Wing upper side: Males shiny blue, wing edge area black, on hind wing often breaking up into separate blotches. Females brown, but especially hind wings also with blue shade. Females’ wing margin with red wavy strip or row of half-moon-shaped blotches.
  • Wing underside: Males pale grey-white. Females’ base colour gingery. Both genders with white-edged black blotches and wing margins with row of red blotches that can also form a continuous strip. Blue blotches outside red blotches.
  • Habitat: Dry pine heaths, rocky outcrops and sandy land, but also bogs.
  • Flying time: Late June–early August.
  • Overwintering form: Egg.
  • Larval foodplant: E.g. heather (Calluna vulgaris), bog bilberry (Vaccinium uliginosum), different Pea family plants (Fabaceae) and Breckland thyme (Thymus serpyllum).

The silver-studded blue is common in central and southern Finland. It can be easily confused with the northern blue and cranberry blue, both of which also have shiny blue blotches on the underside of their hind wings. The silver-studded blue is easy to differentiate, however, because the upper side of its wings have a different kind of pattern. The upper side of males’ wings are bluer than the cranberry blue. The dark margin on the wings is broader and its border is less clearly defined than the northern blue’s. The silver-studded blue’s orange-red area on underside covers a broader area than that on the cranberry blue.

Males fly around looking for females. Females lay their eggs individually on the host plant’s young buds. The following spring the hatching larvae secrete a nourishing, sugary liquid that ants love to lick. This is why ants can often be found around larvae, and their presence protects them.

Other species from the same genus
Other species from the same group

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