Insects of Britain and Ireland: butterflies

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L. Watson and M. J. Dallwitz


Adults. Wingspan (20–)28–48(–52) mm; the fringes conspicuously light-and-dark banded, or not banded. Medium built; short-bodied, or 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, or glabrous. Antennae white-ringed, reaching noticeably less than halfway to the wingtips to reaching about halfway to the wingtips (mostly), or reaching noticeably over halfway to the wingtip (rarely); inserted markedly less than one half the width of the head apart. The antennal clubs gradual-elongate (mostly), or gradual-elongate to abrupt; not curved, or curved to not curved. 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 (85.5–)95–100(–110) degrees. The outer margins convexly curved to more or less straight. Uppersides of the forewings dark brown, or fuscous, or coppery red, or blue, or purple; contrastingly dark-veined (occasionally), or not conspicuously dark-veined (mostly).

Hindwings. Hindwings broadly rounded, or trapezoidal; tailed, or not tailed; the tail filamentous and delicate, or not filamentous; with the outer margins not scalloped (mostly), or with the outer margins scalloped to with the outer margins not scalloped. Uppersides of the hindwings conspicuously dark-veined (occasionally), or not dark-veined; conspicuously patterned (often in females in the form of a subterminal row of small, sometimes faint orange marks bordered with black and/or white), or plain. Uppersides of the hindwings inconspicuously eye-spotted, or not eye-spotted.

Undersides of wings. Undersides of the wings multiply patterned with pale-ringed black spots (commonly), or transversely patterned with numerous pale, sinuous lines (e.g., Lampides), or not multiply patterned with pale-ringed black spots or sinuous lines (the ‘Hairstreaks’).

Undersides of the forewings bright green, or not green. Undersides of the forewings conspicuously dark-veined, or not dark-veined.

Undersides of the hindwings usually multiply spotted with small, dark spots (these often pale-ringed), and often with rows of dark dots embedded in orange spots along the termen; bright green, or not bright green; eye-spotted, or not eye-spotted; with silvery-metallic markings (P. argus), or without metallic markings.

Wing venation. Forewings 11 veined (usually, with vein 7 missing), or 10 veined (when veins 8 and 9 coincide). Forewings with 1 tubular anal vein, or with 2 tubular anal veins; the anal veins of the forewings representing 1b only, or comprising 1b and 1c; vein 1b furcate proximally to simple. Forewings with a discal cell, or without a discal cell. Forewing veins 7 missing, 8 and 9 stalked or coincident.

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 (usually, connate only), or 3+4 proximally joined and 6+7 proximally joined.

Eggs, larvae, pupae. Eggs discoid (mostly), or hemispherical (Lycaena). The larvae characteristically woodlouse-shaped; associated with ants in the later instars (mostly, with varying degrees of intimacy, usually attracting them via a “honey gland” situated in the mid-dorsal line of the 7th abdominal segment), or having no known association with ants (the ‘Hairstreaks’ and Cupido minimus, in which the honey gland is reduced or absent, and Lycaena phlaeas, which lacks it); usually more or less hairy (often densely short-hairy); exposed feeders (rarely), or concealed feeders. Mostly on legumes, but a few on Ericaceae, Labiatae, Cistaceae, Geraniaceae, Ilex, Hedera, Rhamnus, etc., commonly cannibalistic.

Pupae smooth and rounded (usually), or ridged and angular to smooth and rounded (rarely); conspicuously patterned, or plain; without shining-metallic markings; exposed, with no coccoon, or concealed; when ‘exposed’, not suspended, but attached at the tail and secured by a median girdle of silk.

British representation. Genera 19 (3 comprising adventives only); 26 species (including 8 adventive, 2 extinct). Aricia agestis (Brown Argus), Aricia artaxerxes (Durham Argus, Northern Brown Argus, Scotch Brown Argus, Castle Eden Argus), Callophrys rubi (Green Hairstreak), Celastrina argiolus (Holly Blue, Azure Blue), Cupido minimus (Little Blue), Cyaniris semiargus (Mazarine Blue - extinct, now occasionally adventive), Everes argiades (Short-tailed Blue - adventive?), Glaucopsyche alexis (Green-underside Blue, adventive), Lampides boeticus (Long-tailed Blue), Leptotes pirithous (Bloxworth Blue, Lang’s Short-tailed Blue, adventive), Lycaena alciphron (Purple-shot Copper, adventive), Lycaena dispar dispar (Large Copper - the extinct British subspecies), Lycaena hippothoë (Purple-edged Copper, adventive), Lycaena phlaeas (Small Copper), Lycaena tityrus (Sooty Copper, adventive), Lycaena virgaureae (Scarce Copper, former resident but extinct since about 1850), Lysandra bellargus (Adonis Blue), Lysandra coridon (Chalk-hill Blue), Maculinea arion eutyphron (Large Blue, the perhaps extinct British subspecies), Neozephyrus (Quercusia) quercus (Purple Hairstreak), Plebejus argus (Silver-studded Blue), Plebicula dorylas (Turquoise Blue, adventive), Polyommatus icarus (Common Blue), Satyrium (Strymonidia) pruni (Black Hair-streak), Satyrium (Strymonidia) w-album (White-letter Hairstreak), Thecla betulae (Brown Hairstreak).

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

Comments. Small, often brightly coloured butterflies; flight quick and agile but seldom sustained, hence often represented by localised colonies. With the exceptions of the ‘Hairstreaks', Lycaena phlaeas and Cupido minimus, the life histories of British Lycaenidae involve symbiotic relationships with ants, which “milk” the larvae from their honey glands. The presence of ants around the larvae on their foodplants evidently serves to deter potential insect parasites and predators, and in some cases the relationship involves deliberate “farming” of the larvae by their protectors. In Britain, ants have been observed to carry larvae of Lysandra coridon and Plebajus argus in their jaws and deposit them on the approriate foodplants conveniently near their nests; and in the famous case of the Large Blue (Maculinea arion), the butterfly larvae are virtually parasitic, being taken into the ants’ nest and fed to maturity on their own larvae. For detailed discussion, see Ford (1945).

Classification. Superfamily Papilionoidea.

Illustrations. • Lycaenidae (1), Hairstreaks and Coppers: Newman, 1871. • Lycaenidae (2), Blues: Newman, 1871. • Lycaenidae (3), Blues cont.: Newman, 1871. • Maculinea arion (Large Blue) larva carried by ant (Frohawk).

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.’.