Insects of Britain and Ireland: butterflies

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L. Watson and M. J. Dallwitz


Adults. Wingspan 78–108 mm; the fringes conspicuously light-and-dark banded. Slender-bodied to medium built; very short-bodied. The eyes glabrous. Antennae reaching noticeably less than halfway to the wingtips. The antennal clubs somewhat gradual-elongate; curved; slightly flattened to not flattened (blunt, not pale-tipped). Labial palps ascending (appressed to frons). Having all 6 legs fully developed and operational for walking. Fore-legs with a tibial epiphysis. Tibiae of middle legs without spurs. Posterior tibiae 2-spurred.

Forewings. Forewings apically blunt. The outer and hind margins angled at about 100–115 degrees. The outer margins convexly curved to concavely curved, or sigmoid-curved (slightly). Uppersides of the forewings yellow; contrastingly dark-veined; without a discal mark; with a large basal patch irrorated yellow, three black transverse blotches beneath the costa posteriorly, a black subterminal band often irrorated yellow, a narrow black terminal fascia, and black venation.

Hindwings. Hindwings broadly rounded (the inner margin concave); conspicuously long- tailed; with the outer margins scalloped. Uppersides of the hindwings yellow; conspicuously dark-veined; conspicuously patterned. Uppersides of the hindwings conspicously eye-spotted. The eye-spots 1; near the tornus. Uppersides of the hindwings with a conspicuous discal mark (represented by blackening over the transverse vein); coloured and patterned somewhat like the fore-wings, but the black subterminal band enclosing blue spots, and with a red and blue tornal eye-spot.

Undersides of wings. Undersides of the forewings complexly colour-patterned as a pallid duplication of the upperside; conspicuously dark-veined.

Undersides of the hindwings complexly colour-patterned as a pallid duplication of the upperside; conspicuously dark-veined; eye-spotted. The eye-spots 1; near the tornus. Undersides of the hindwings without a discal mark.

Wing venation. Forewings 13 veined; without basally dilated veins. Forewings with 1 tubular anal vein; the anal veins of the forewings representing 1b only; vein 1b simple. Forewings with a discal cell; vein 2 departing from the cell less than three-quarters of the distance from its base (from about halfway). Forewing veins 8 out of 7 (i.e., 7 and 8 stalked), 9 connate with 7, 10–12 separate, the transverse vein angulated on 5.

Hindwings 8 veined; with a praecostal spur; with 1 anal vein; lacking vein 1a; the anal veins representing 1b only. Hindwings with a closed discal cell; the transverse vein complete. 7 veins arising from the hindwing cell. The cell-derived hindwing veins all arising independently of one another.

Eggs, larvae, pupae. Eggs sub-globular; more or less smooth. The larvae hairless; with a pair of tentacles from segment 2 (these orange-coloured and fleshy, constituting the V-shaped, retractile ‘osmaterium’); exposed feeders; not feeding in communal tents. On Umbelliferae - Heracleum, Angelica, etc.

Pupae rather ridged and angular; conspicuously patterned (black-dotted); without shining-metallic markings; exposed, with no coccoon; not suspended, but attached at the tail and secured by a median girdle of silk.

British representation. 1 species. Papilio machaon (Swallow-tail). The adults abroad May to August.

Status in Britain. Indigenous (the endemic British subspecies, P. machaon britannicus), or rare ocurrence representing occasional, genuine immigrants (referring to the continental subspecies, P. machaon gorganus). The British subspecies, once widespread in the east of England, was almost exterminated by drainage of the fens and is now confined the Norfolk Broads. Specimens are more or less convincingly distinguishable from the mainland-European subsp. gorganus by the heavier dark lines along the forewing nervures, and by the wider, dark submarginal band of the forewings being relatively broader towards the inner margin (see accompanying photos). The endemic British race further differs in its habitat requirements, being confined to fen country. Its mainland counterpart has no such limitation.

Distribution. East Anglia and southeast England. Frequenting open places. Habitats calcareous and non-calcareous.

Comments. Flight strong and sustained, sometimes gliding.

Classification. Superfamily Papilionoidea. Papilionidae.

Illustrations. • Papilio machaon (Swallow-tail: British and mainland-European subspecies): photos. • Papilio machaon (Swallow-tail: Hübner/Curtis). • Swallow-tailed and Apollo: Newman, 1871. • Larva and pupa of P. machaon: 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.’.