Insects of Britain and Ireland: butterflies
Adults. Wingspan 29–38 mm; the fringes not banded. Medium built; short-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 to pointed. The outer and hind margins angled at about 95 degrees. The outer margins convexly curved, or convexly curved to more or less straight. Uppersides of the forewings in the female, dark fuscous, or purple and fuscous (somtimes suffused deep purple-blue), or blue (bright lilac-blue in the male); with a conspicuous discal mark (in the form of a small dark spot), or without a discal mark; in the male plain bright lilac-blue apart from the blackish terminal edge; in the female dark fuscous more or less suffused with deep purplish-blue, with a subterminal series of small orange spots (sometimes obscure), each of which which may be pale- or dark-ringed or include a dark spot.
Hindwings. Hindwings with the outer margins not scalloped. Uppersides of the hindwings in the female, dark fuscous, or purple and fuscous (somtimes suffused deep purple-blue), or blue (bright lilac-blue in the male); conspicuously patterned (often, in the female), or plain; without a discal mark; in the male plain bright lilac-blue apart from the blackish terminal edge; in the female dark fuscous more or less suffused with deep purplish-blue, often with a subterminal series of small orange spots each of which which may be pale- or dark-ringed or include a dark spot; i.e., similar to the forewings, but the row of terminal spots in the females is often 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 white-ringed black spots representing the discal mark, a postmedian series about 6 of them, and often two more anteriorly; plus a double series of dark fuscous white-ringed spots subterminally, these separated by dark orange spots which can be inconspicuous or obsolete; with two black spots before the middle.
Undersides of the hindwings pale ochreous-grey or light brownish, with white-ringed black spots representing the discal mark, a postmedian series of them, and three more anteriorly; plus a double series of dark fuscous white-ringed spots subterminally, these separated by dark orange spots which are more conspicuous than those under the forewings; with a subterminal row of orange spots which are apposed to terminal black dots; with a conspicuous discal mark; without metallic markings (the obvious diffence from P. argus); with orange 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; short- hairy. On herbaceous legumes.
Pupae smooth and rounded; conspicuously patterned; exposed, with no coccoon, or concealed (sometimes in a slight cocoon).
British representation. 1 species. Polyommatus icarus (Common Blue). The adults abroad May to September.
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. • Polyomatus icarus (Common Blue): photos. • Polyomatus icarus (Common Blue): egg, larva, pupa. • Polyommatus icarus (Common Blue: Hübner/Curtis).
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’.