About Polyura arja (Felder, 1866)
This species has the scientific name Polyura arja (Felder, 1866). Polyura arja reaches a wingspan of 75–80 millimetres (3.0–3.1 in). The outer edge of its forewings is concave, and the hindwings have two short blue tails. The upperside of the wings is brown, with a broad white or anteriorly pale green band running from the inner edge of the forewing to the costal edge of the hindwings. There are one or two small white spots at the apex of the forewings, and a continuous row of white or pale yellow spots along the outer submargin of the hindwings. The underside of the wings is lighter brown, with a pattern quite similar to that of the upperside. The body is dark brown.
According to Seitz's description, this is an exclusively continental species with pronounced seasonal dimorphism. It is distinguished from Polyura athamas by the distinctive pale greenish white discal blotches on the upper wing surface. On the underside, the black submarginal striae are surrounded by a broader, pale greyish-white shade, and the transcellular spot on the forewings is always larger.
vernus R. and J. (134 a) is the name for the extreme dry-season form, where pale colouring dominates the pattern. roeberi Fruhst. (134 a) is the larger-sized extreme rainy-season form, which has a broadly black border. arja Fldr. is the most common intermediate form, with a broader median area than roeberi. Hans Fruhstorfer only personally knew roeberi from Assam, while vernus and arja occur from Sikkim to Tenasserim. Specimens can be found from May to October, and are present throughout the year in hot valleys according to Niceville. Fruhstorfer collected multiple specimens at Chiem-Hoa (Tonkin) in August, and has also seen small-sized specimens from Petjaburi (Siam). This species is distributed in northeast India (from Sikkim to Assam), Burma, Thailand, and Indochina.
