Insects of Britain and Ireland: the families of Lepidoptera

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L. Watson and M. J. Dallwitz



Adults diurnal; very large; relatively very short-bodied; relatively slender-bodied (wingspan more than 15 times the thoracic width) to medium built (wingspan more than 8 and less than 15 times the thoracic width); wings in repose apposed vertically over the back.

Head rough. Antennae very short; extending to about 0.3–0.4 times the length of the forewing; inserted markedly less than one half the width of the head apart; clubbed. The club gradual (curved, blunt, not flattened, briefly pale-tipped). The club curved. Antennae of males simple; non-ciliate. Eyes glabrous. Ocelli absent. Chaetosemata present. Maxillary palps much reduced; 1 segmented. Labial palps ascending; 3 segmented. Proboscis fully developed; not scaly.

Wingspan 90–120 mm; 12–15 times the thoracic width. Forewings broad; about 1.7–1.8 times as long as wide. The outer and hind margins angled at about 110 degrees. The outer margin concavely curved; forewings apically blunt; ground colour predominantly orange-brown; forewings without eye-spots above; forewings not eye-spotted underneath near the tip. Hindwings broadly rounded; similar in breadth to the forewings; the upper surfaces conspicuously patterned above; with neither discal spot nor transverse lines (with the conventional lepidopterous lines and discal marks lacking or more or less obscured); without a frenulum.

Neuration of forewings and hindwings dissimilar. Forewings 12 veined; without basally dilated or vesicular veins; with 1 anal vein. The anal veins of the forewings representing 1b only. Forewings lacking a tubular vein 1c. Vein 1b of the forewings simple. Discal cell of the forewings without a tubular media (M) vein. Forewing veins 8 and 9 out of 7, 10 connate with or from near the base of 7, 11 from the distal front of the cell, 12 free. Hindwings 9 veined; with 2 anal veins. The anal veins of the hindwings comprising 1a and 1b. Hindwings exhibiting vein 1a; lacking a tubular vein 1c; with a praecostal spur. The hindwing cell emitting more than six veins. 7 veins arising from the hindwing cell. The cell-derived hindwing veins 3+4 proximally joined. Vein 8 of the hindwings arising from the upper margin of the cell (from near its base); not approximating to vein 7.

Adults having only 4 fully developed legs. Fore-legs of female useless for walking. Fore-legs without a tibial epiphysis (with the fore tarsus of the female differing from that of the male in ending in a spiny knob). Tibiae of middle legs 2-spurred. Posterior tibiae 2-spurred.

Tympanal organs absent.

Eggs, larvae and pupae. Eggs not flattened (shortly truncate-fusiform); ribbed and/or reticulate (with about 20 longitudinal ribs and numerous fine cross-linking ribs). Larval prolegs 10. Larvae with a pair of tentacles from segment 2 (these non-retractile, and another, shorter pair on segment 12); without bristly spines; exposed feeders; not feeding in communal tents. On Asclepiadaceae and Apocynaceae.

Pupae smooth and rounded; conspicuously patterned; with shining-metallic spots; exposed, with no coccoon; suspended from the tail (cremaster), with no median silk girdle.

British representation. Genera 1; 1 species. Danaus plexippus (Milkweed, Monarch), adventive.

Classification. Butterflies. Suborder Ditrysia. Superfamily Papilionoidea.

Comments. Famous migratory butterflies, distasteful to predators.

Illustrations. • Danaus plexippus (Milkweed, Monarch: Morris).

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Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2003 onwards. Insects of Britain and Ireland: the families of Lepidoptera. Version: 8th June 2016.’.