Insects of Britain and Ireland: butterflies

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L. Watson and M. J. Dallwitz


Adults. Wingspan 40–52 mm (P. napi), or (35–)40–58 mm (rapae, noted for occasional dwarfism), or 60–76 mm (brassicae). The wings opaque. The fringes conspicuously light-and-dark banded to not banded (P. napi), or not banded. Slender-bodied to medium built; short-bodied. The eyes not white-rimmed; glabrous. The head and antennae not rosy-tinged. Antennae reaching noticeably less than halfway to the wingtips. The antennal clubs abrupt; flattened (blunt, pale-tipped). Labial palps ascending (appressed to the frons). 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 97–105 degrees. The outer margins convexly curved to more or less straight. Uppersides of the forewings white, or cream; contrastingly dark-veined (often, in P. napi only), or not conspicuously dark-veined; without a discal mark (i.e., excluding the blackish forewing spots of males); blackish around the apex and sometimes towards the middle of the inner margin, and often with two blackish spots aligned one above the other towards the outer margin, the latter being faint or lacking in some males.

Hindwings. Hindwings broadly rounded. Uppersides of the hindwings white, or cream; conspicuously dark-veined (often, in P. napi only), or not dark-veined; fairly conspicuously patterned (with grey outlining of the veins in P. napi), or plain (apart from a dark costal mark near the apex, which is a constant feature of all three species); without a discal mark; white like the forewings, blackish basally, and with the blackish mark towards the apex of the costa.

Undersides of wings. Undersides of the forewings white or creamish, differing from the uppersides in the blackish apical component being replaced with creamish, and in the males of P. brassicae and P. rapae consistently exhibiting relatively large versions of the post-median black spot (even when this is lacking or obsolete on the upperside; conspicuously dark-veined (in P. napi only), or not dark-veined.

Undersides of the hindwings creamier than the upperside, suffused blackish towards the base; conspicuously dark-veined (in P. napi only), or not dark-veined; without a discal mark.

Wing venation. Forewings 11 veined; without basally dilated veins. Forewings with 1 tubular anal vein; the anal veins of the forewings representing 1b only (but P. brassicae can exhibit a faint 1c); 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 halfway or a little beyond). Forewing veins 2–5 separate from the cell; 6 and 7 on a long stalk, then a short 8 distally from 7 (P. brassicae, P. napi, or apparently lost (P. rapae), 9 and 10 separate from near the distal end of the cell, 11 free (Meyrick interprets this layout as “9 absent”). “The subcostal nervure 4-branched” (Kirby).

Hindwings 9 veined, or 10 veined; with a praecostal spur; with 2 anal veins, or with 2 anal veins to with 3 anal veins (P. brassicae exhibiting a conspicuous but scarcely “tubular” 1c); exhibiting vein 1a; the anal veins comprising 1a and 1b. 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 broadly bottle-shaped; longitudinally ribbed. The larvae associated with ants in the early instars (attracting them via secretions presented at the forked tips of long glandular setae), or having no known association with ants (Pieris brassicae, in which the setae are apparently non-secretory); hairy; exposed feeders. On Cruciferae, Resedaceae and Tropaeolaceae.

Pupae ridged and angular; conspicuously patterned, or plain (but usually fairly conspicuously black-dotted or streaked); 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. 3 species. Pieris brassicae (Large White), Pieris rapae (Small White), Pieris napi (Green-veined White). The adults abroad April, or May to October.

Status in Britain. Indigenous (supplemented sometimes by large-scale immigration).

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 (especially P. napi), or open places. Habitats calcareous and non-calcareous.

Comments. Flight irregular, fluttering.

Classification. Superfamily Papilionoidea. Pieridae.

Illustrations. • Pieris brassicae (Large White), P. napi (Green-veined White) and P. rapae (Small White): Hübner. • Pieris brassicae (Large White, Large Cabbage White): photos. • Pieris brassicae (Large White, Large Cabbage White: Hübner/Curtis). • Pieris brassicae and Pieris napi: as Pontia, Stephens (1828. • Pieris brassicae (Large White, Large Cabbage White): egg, larva, pupa. • Pieris rapae (Small White, Small Cabbage White: Hübner/Curtis). • Larvae and pupae of P. brassicae, P. napi, P. rapae: Duponchel (1849). • Pieris rapae (Small White, Small Cabbage White): egg, larva, pupa. • Pieris napi (Green-veined White): photos. • Pieris napi (Green-veined White: Hübner/Curtis). • Pieris napi (Green-veined White): egg, larva, pupa. • Pieridae (3): Newman, 1871.

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.’.