About Elymnias hypermnestra Linnaeus, 1763
Like other species in the genus Elymnias, the common palmfly (Elymnias hypermnestra Linnaeus, 1763) has a precostal cell in the hindwings, plus a tuft of androconial scales on the dorsal discal cell of the hindwings. Some populations of this butterfly species are sexually dimorphic, meaning males and females do not resemble one another. In sexually dimorphic populations, males have black upper forewings marked with small blue patches and mimic species in the genus Euploea, while females mimic butterfly species in the genus Danaus. The race undularis, found in the Subhimalayas and Southeast Asia, has a blackish brown upperside in males. The male forewing bears a subterminal series of elongate blue, or sometimes slightly green, spots. This series curves strongly inwards, growing more elongated opposite the apex, and forms an almost oblique bar that extends up to the costa. On the male hindwing, the terminal margin is broadly bright chestnut, sometimes with a paler subterminal spot in two or more interspaces. The underside is pale brown: the basal two-thirds of both the forewing and hindwing are densely covered with broad, dark ferruginous transverse striae, while the outer third is more sparsely covered with these striae. The forewing has a broadly triangular pale purplish-white preapical mark; both forewings and hindwings have a broad purplish-white subterminal area. The hindwing has a small white spot opposite the middle of the costa, plus a more or less complete series of more obscure whitish subterminal spots. Antennae, head, thorax and abdomen are brown, with the underside of the abdomen paler. Females of race undularis have a tawny upperside, with black veins. On the female forewing, the dorsal margin is broadly black; the apical area beyond a curved line running from the tornus, around the apex of the cell and slightly beyond it, to the base of the costa is also black. The wing is crossed preapically by a conspicuous, broad, oblique white bar, plus three subterminal white spots. On the female hindwing, the dorsal margin is dusky; the terminal area is broadly black, and the costal margin is more narrowly black; there is a subterminal series of four white spots. The female underside is tawny, with similar markings to the male; pale whitish markings are more extensive, and the broad dorsal margin has no striae. Race fraterna Butler, found in Sri Lanka, is an insular representative of E. undularis. Males differ from race undularis males on the upperside by the more or less complete absence of the subterminal and preapical blue markings on the forewing, and the broad terminal border of the hindwing being a much brighter, almost ochraceous chestnut. On the underside, pale markings are somewhat restricted. Overall, males of race fraterna very closely resemble males of E. undularis on both the upper and underside. This species occurs across Peninsular India, sub-Himalayas, and Southeast Asia. Its recorded food plants are Cocos nucifera (coconut), Calamus pseudo-tenuis, Calamus rotang, Calamus thwaitesii, Phoenix loureiroi, and Licuala species.
