Insects of Britain and Ireland: butterflies

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L. Watson and M. J. Dallwitz


Adults. Wingspan 38–45 mm; the fringes conspicuously light-and-dark banded (on the hindwings), or conspicuously light-and-dark banded to not banded. Medium built; short-bodied to 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 reaching noticeably less than halfway to the wingtips to reaching about halfway to the wingtips. The antennal clubs gradual-elongate. 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 95–100 degrees. The outer margins only slightly convexly curved to more or less straight. Uppersides of the forewings dark brown; with a conspicuous discal mark (this blackish); in the female with a postmedian orange band falling short of costa and termen, this reduced in the male to one or two obscure orange spots.

Hindwings. Hindwings broadly rounded, or trapezoidal; shortly tailed (via a projection from vein 2, and adjoining a tooth from vein 3); the tail filamentous and delicate to not filamentous; with the outer margins scalloped (towards the tornus). Uppersides of the hindwings dark brown; fairly conspicuously patterned (in the female), or plain (in the male); without a discal mark; plain apart from two or three terminal orange spots towards the tornus, these less conspicuous in the male.

Undersides of wings. Undersides of the wings not multiply patterned with pale-ringed black spots or sinuous lines.

Undersides of the forewings a quite bright brownish orange with a black discal mark and a postmedian white, anteriorly black-edged line from the costa. Undersides of the forewings not green.

Undersides of the hindwings a quite bright brownish orange with a postmedian white, anteriorly black-edged line from the costa, another similar, shorter line medianly from the costa, and the termen deeper orange towards the tornus; without a discal mark; with two sharply defined white lines.

Wing venation. Forewings 10 veined, or 11 veined. Forewings with 1 tubular anal vein; the anal veins of the forewings representing 1b only; vein 1b furcate proximally to simple. Forewing veins 7 missing, 8 and 9 stalked or coincident, 6 out of 9.

Hindwings 9 veined; without a praecostal spur; with 2 anal veins; exhibiting vein 1a; the anal veins comprising 1a and 1b. 7 veins arising from the hindwing cell. The cell-derived hindwing veins 3+4 proximally joined (connate only).

Eggs, larvae, pupae. Eggs discoid to hemispherical (depressed-spheroid); reticulate. The larvae woodlouse-shaped; having no known association with ants. On Blackthorn.

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. Thecla betulae (Brown Hairstreak). The adults abroad August and September.

Status in Britain. Indigenous.

Distribution. 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. • Thecla betulae (Brown Hairstreak). • Thecla betulae (Brown Hairstreak): egg, larva, pupa. • Larva and pupa of T. betulae: Duponchel (1849).

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.’.