Insects of Britain and Ireland: butterflies

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L. Watson and M. J. Dallwitz


Adults. Wingspan 33–38 mm; the fringes conspicuously light-and-dark banded (but less conspicuously so in worn males). 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. The antennal clubs more or less gradual-elongate, or abrupt (tapered); 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. The outer and hind margins angled at about 90–95 degrees. The outer margins convexly curved. Uppersides of the forewings lilac-tinged blue (in the male, paler in the female); with a conspicuous discal mark, or without a discal mark (then this very small, dark); plain or tending to fuscous-shaded around the apex in the males, with a dark fuscous terminal band in the females.

Hindwings. Hindwings broadly rounded; with the outer margins not scalloped. Uppersides of the hindwings lilac-tinged blue (in the male, paler in the female); conspicuously patterned (in the female), or plain (in the male); without a discal mark; plain in males, those of the females with small dark, pale-encircled spots before the termen and in the second brood with a dark fuscous band alongside the costa.

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

Undersides of the forewings whitish-blue, with a postmedian series of small black, shortly-elongate, pale-edged marks.

Undersides of the hindwings whitish-blue, with a postmedian series of small black, pale-ringed dots and additional spots anteriorly and on the inner disc; with neither orange spots nor an orange band; with a conspicuous discal mark (a black dot), or without a discal mark; without 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), or 3+4 proximally joined and 6+7 proximally joined (connate). Hindwing veins 2, 3 and 4 from one stalk, 5 separate and fairly conspicuous 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; warty and hairy. Usually on Ilex (first brood) and Hedera (second brood).

Pupae smooth and rounded; conspicuously patterned; exposed, with no coccoon; not suspended, but attached at the tail and secured by a median girdle of silk.

British representation. 1 species. Celastrina argiolus (Holly Blue, Azure Blue). The adults abroad April, or May (first brood), or August (second brood).

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 woodland and open places. Habitats calcareous and non-calcareous.

Classification. Superfamily Papilionoidea. Lycaenidae.

Illustrations. • Celastrina argiolus subsp. britanna (Holly Blue: photos). • Celastrina argiolus (Holly Blue: Giles Watson, photos). • Celastrina argiolus (Holly Blue): egg, larva, pupa.

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.’.