About Prosotas aluta (Druce, 1873)
This description covers the race coelestis of Prosotas aluta. For the male: the upperside is shining bluish with a purple flush visible in certain lights. Both the forewings and hindwings have a narrow fuscous black edge along the termen; the jet-black anteciliary line on each wing is obscurely visible on this edging, and the fuscous black edging is slightly widened anteriorly. The underside is dusky brown. On the forewing, a transverse, subbasal, broad, dark brownish-black band with white margins runs from the subcostal to vein 1; a similar band along the discocellulars also extends to vein 1. An upper discal band of the same type starts from the costa, curves slightly outwards, and stops short at vein 3. This is followed by a postdiscal transverse series of dark spots, which are comparatively broadly edged with white on the inner side, and very slenderly edged with white on the outer side. After the spots comes a subterminal extremely slender series of transversely linear spots, a white line, and a jet-black anteciliary line; the cilia are brown. On the hindwing, there are three transversely arranged dark brownish-black spots. Transverse subbasal and discal bands of the same colour are present; both bands are edged with slender white lines on their inner and outer sides, and the discal band is greatly and irregularly widened in the middle, where a snow-white transverse spot lies on the dark background. Beyond these bands, there is a postdiscal series of comparatively broad white lunules, a subterminal very slender white lunular line, a terminal white thread, and a jet-black slender anteciliary line. The cilia are shining silky brown, and the tail is brown with a white tip. The antennae are black, with shafts obscurely speckled with white; the head is black; the thorax and abdomen are bluish. On the underside, the palpi have a blackish fringe, and the thorax and abdomen are whitish. This butterfly species is found in India from Kumaon to Assam, extending into Myanmar, and also occurs in the Andaman Islands. In Southeast Asia, its range extends from Myanmar to southern Yunnan, and southwards to Peninsular Malaysia, Borneo, Sumatra, Nias, northern Sulawesi, the Philippines, Thailand, Singapore, and Vietnam; it is also found in China, Nepal, Bhutan, and Bangladesh.
