Byasa latreillei, the rose windmill, is a butterfly from the windmills genus, found in various parts of Asia, comprising tailed black swallowtail butterflies with white spots and red submarginal crescents.
Hindwing has a white discal band consisting of elongated spots in veins 2, 3 and 4.
The female has an additional small spot in vein 5 and only half way to vein 6.
It also has a series of lunules in veins 2 to 5 along the margin. The lunules in veins 2 to 4 are rose coloured while the lunule in vein 5 is white.
The male has a white scent wool brand in a dorsal fold..
The male can be said to resemble the common rose, and, the female, the common Mormon form stichius..
Male upperside dull brownish black. Forewing with streaks in cell, the internervular streaks and the veins velvety black. Hindwing: ground colour more uniform to apex of cell, beyond this interspaces 2, 3 and 4 with broad elongate white spots, the spot in interspace 2 slightly tinged outwardly with crimson; sometimes a white crimson-tinted spot also in interspace 1; a subterminal series of crimson lunules in interspaces 2 to 5, that in 5 generally more or less white; lastly, a crimson spot at apex of vein 3 and on apex of tail. Underside similar, ground colour much paler; markings of the hindwing as on the upperside, but slightly larger, the crimson spots brighter; in many specimens a small discal adnervular spot in interspace 5, and a sub-terminal small white lunule in interspace 6 also present; the crimson-tinted discal spot in interspace 1 always present. Antennae dark brownish black, head and front of the prothorax crimson, the rest of the body above black; beneath, the palpi, thorax and abdomen crimson, the middle of the thorax and of the abdomen with black markings. Female similar, slightly paler; the white and crimson markings on the hindwing on both upper and undersides similar but larger; there is generally also a discal adnervular spot in interspace 5. Antennae, head, thorax and abdomen as in the male.
Caterpillar - The larva is brownish to pale purple in colour. The larva has a shiny black head and a white obliquely-placed band on segments seven and eight. It has a large number of tubercles. The first six segments of the larva have one pair of tubercles; the seventh to tenth segments have three pairs each; the eleventh to thirteen segments each have two pairs of short tubercles. The tubercles are purple, have red tips and streaks on the base.
The pupa is reddish orange in colour and relatively broad in shape. It is attached by a body band. The pupa emits a squeak when touched.
Habits
It flies in May and June. It flies between in Garhwal and between further east at Chungthang, north Sikkim in the Teesta valley.
