About Ideopsis vulgaris (Butler, 1874)
Ideopsis vulgaris, commonly called the blue glassy tiger, is a butterfly species first described by Butler in 1874. Adults of this species have a wingspan of 70 to 80 millimetres (2.8–3.1 in). This species is very similar in appearance to Parantica agleoides, the dark glassy tiger. It can be distinguished from the dark glassy tiger by a transverse black bar located in the forewing cell that cuts through one of the white streaks. Like other milkweed butterflies, Ideopsis vulgaris is mimicked by Chilasa clytia, a member of the Papilionidae family. On the upperside of the wings, the base color is black. The dorsal margin of the hindwing is broadly cinereous, and both wings have subhyaline bluish-white streaks and spots. On the forewing, these markings include: a short streak along the dorsal margin; two broad streaks that are united at the base in interspace 1, with the upper streak curved; a broad streak in the cell, with an outwardly indented detached spot beyond it in the apex; a slender costal streak; two large discal spots that are pointed inward and truncate outward; three elongate spots beyond the apex of the cell; four or five elongate preapical spots beyond those; and finally a subterminal and a terminal series of spots that decrease in size towards the apex of the wing. On the hindwing, markings include: elongate streaks in interspaces 1a and 1b; two streaks in interspace 1; two streaks in the cell with a short, slender oblique streak between their apices; shorter streaks that radiate outwards in interspaces 2 to 6; a subterminal series of small spots; and a terminal row of dots beyond that. The underside of the wings is similar in pattern to the upperside, but all markings are better defined. The antennae are black. The palpi are black on the upper side and bluish white on the lower side. The head and thorax are black, with bluish white spots. The abdomen is brown on the upper side and sullied white on the lower side. Males have no specialized sex markings on the wings. Two named geographic races are recognized. Race exprompta Butler is found in Sri Lanka. It closely resembles the nominal subspecies Ideopsis vulgaris vulgaris, but all of its markings are much broader, the apical spot in the forewing cell is less outwardly emarginate. On the hindwing, interspaces 1a and 1b are entirely filled with white streak, and the short slender streak that lies between the apices of the two streaks in the cell coalesces with the lower streak. Race nicobarica W.-M. & de N. occurs in the Nicobar Islands. It is similar to race exprompta, but its subhyaline markings are even broader and somewhat blurred. On the upperside of the forewing, the entire basal two-thirds of interspace 1 is bluish white, enclosing a fine longitudinal black line, and the streak in the discoidal cell is very broad, occasionally extending to the apical spot in the cell. On the hindwing, the black in interspace 1 is reduced to just a narrow streak, and the entire cell is bluish white, crossed lengthwise by a faint, forked black line; in the single male specimen held in the British Museum collection, this line is completely absent. This species is distributed across India, Sri Lanka, Singapore, Thailand, Laos, Vietnam, Hainan, South Burma to Sundaland, Sumatra, Java, the Lesser Sunda Islands to Alor, and Borneo to Palawan. These butterflies occupy a range of habitats, and are especially common at rainforest edges, the edges of plantations, and in coastal mangrove areas.
