Insects of Britain and Ireland: the families of Lepidoptera
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).
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. 2003 onwards. Insects of Britain and Ireland: the families of Lepidoptera. Version: 8th June 2016. delta-intkey.com’.