Insects of Britain and Ireland: butterflies

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L. Watson and M. J. Dallwitz

Plebejus

Adults. Wingspan 27–33 mm; the fringes conspicuously light-and-dark banded to not banded. Medium built; medium-bodied. The eyes white-rimmed; notched or emarginate at the bases of the antennae and contiguous with the bases of the antennal sockets; hairy. Antennae white-ringed, reaching noticeably less than halfway to the wingtips to reaching about halfway to the wingtips. The antennal clubs gradual-elongate (tapered); curved; not flattened. Labial palps ascending. Having all 6 legs fully developed and operational for walking. Fore-legs without a tibial epiphysis. Tibiae of middle legs 2-spurred. Posterior tibiae 2-spurred.

Forewings. Forewings apically blunt, or blunt to pointed. The outer and hind margins angled at about 95–100 degrees. The outer margins convexly curved. Uppersides of the forewings in the female dark brown, or fuscous, or blue to purple (in the male); contrastingly dark-veined, or contrastingly dark-veined to not conspicuously dark-veined; with a conspicuous discal mark to without a discal mark (this small and dark if detectable); in the male, purplish-blue terminally suffused dark fuscous; in the female dark, iridescent brown-fuscous, usually with a subterminal series of more or less obscure orange crescentic spots each enclosing a black dot.

Hindwings. Hindwings broadly rounded. Uppersides of the hindwings in the female dark brown, or fuscous, or blue to purple (in the male); conspicuously dark-veined, or conspicuously dark-veined to not dark-veined; conspicuously patterned; without a discal mark; in the male, purplish-blue terminally suffused dark fuscous; in the female dark, iridescent brown-fuscous, usually with a subterminal series of orange crescentic spots each enclosing a black dot; i.e., similar to the forewings, but the orange spots usually brighter.

Undersides of wings. Undersides of the wings multiply patterned with pale-ringed black spots.

Undersides of the forewings pale ochreous-grey or light brownish, with a white-ringed black spot representing the discal mark, a postmedian series of 6 or 7 white-ringed black spots, and a double series of dark fuscous white-ringed spots subterminally, the latter separated by dark orange which is less conspicuous than on the hindwings or obsolete; with no black spots before the middle.

Undersides of the hindwings undersides pale ochreous-grey or light brownish, with a white-ringed black spot representing the discal mark, a postmedian series of white-ringed black spots, three similar anterior spots, and a double series of dark fuscous white-ringed spots subterminally, these separated by dark orange which is more conspicuous than on the forewings, and further embellished with a conspicuous series of metallic silvery-blue spots situated posteriorly beyond the orange band; with a subterminal row of orange spots which are apposed to terminal black dots; with a conspicuous discal mark; with silvery-metallic markings.

Wing venation. Forewings 11 veined. Forewings with 1 tubular anal vein; the anal veins of the forewings representing 1b only; vein 1b simple. Forewings with a discal cell to without a discal cell (the transverse vein very faint); vein 2 departing from the hind margin of the cell in its distal quarter to departing from the cell less than three-quarters of the distance from its base (from at least 2/3 out). Forewing vein 5 conspicuous from the base and traversing the faint transverse vein, 6 separate, 7 and 8 long-stalked with 8 very short to the costa, 9–11 separate from the cell.

Hindwings 9 veined; without a praecostal spur; with 2 anal veins; exhibiting vein 1a; the anal veins comprising 1a and 1b. Hindwings with a closed discal cell to without a closed discal cell; the transverse vein vestigial only to lacking. The cell-derived hindwing veins 3+4 proximally joined (connate). Hindwing veins 2, 3 and 4 from one stalk, 5 separate and absent or vestigial proximal to the faint transverse vein, 8 separate and sharply curved along the costa.

Eggs, larvae, pupae. Eggs discoid; densely spinulose. The larvae woodlouse-shaped; associated with ants in the later instars. On divers heathland dicots - Ornithopus, Ulex, Calluna, etc.

Pupae smooth and rounded; conspicuously patterned; exposed, with no coccoon to concealed (? - “usually unattached, sometimes subterranean”).

British representation. 1 species. Plebejus argus (Silver-studded Blue). The adults abroad July and August.

Status in Britain. Indigenous.

Distribution. Northern Scotland, southern Scotland, northern England, English Midlands, East Anglia, Wales, southeast England, central southern England, southwest England, Isle of Wight, and Ireland. Frequenting open places. Habitats calcareous and non-calcareous.

Classification. Superfamily Papilionoidea. Lycaenidae.

Illustrations. • Plebejus argus (Silver-studded Blue): photos. • Plebejus argus (Silver-studded Blue): egg, larva, pupa. • Larvae and pupae of P. argus: Duponchel (1849). • Aricia, Lysandra, Maculinea, Plebejus, Polyommatus (Blues: Coleman, 1860).


To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2008 onwards. Insects of Britain and Ireland: butterflies. Version: 16th May 2016. delta-intkey.com’.

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