Introduction
The Sailors, or Gliders as they are sometimes called, are all members of the genus Neptis – a large and confusing group of butterflies found across much of the world, excluding the Americas. They are noted for their characteristic sailing flight, and their shared theme of white spots and bars on a black background. They are closely allied to Pantoporia, in which the white markings are replaced by orange; and to Athyma which look like Neptis but have more triangular forewings.
The genus Neptis comprises of about 170 species, of which at least 65 occur in Africa, 40+ in the Palaearctic region ( Europe, and Asia north of the Himalayas ), 6 in Australia / New Guinea, and about 50 in the Oriental region. About 16-18 of the latter are found in Malaysia. Distinguishing the species involves careful study of the configuration of the white spots, bars and submarginal lines on both wing surfaces.
Neptis duryodana is found in West Malaysia, Sumatra, Sarawak, Brunei, Sabah, Kalimantan, Java and Palawan.
Habitats
This species is found in forested habitats at elevations between sea level and about 500 metres. It is found in both primary and secondary forest, frequenting sunlit glades and forest edge habitats.
Lifecycle
The lifecycle appears to be unrecorded but will be similar to that of other Neptis species – the egg will be placed at the very tip of a leaf of the foodplant, on the upper surface. It will be pale green, globular, and covered in a network of hexagonal ridges from which arise 100 or more tiny spikes, giving it the appearance of a tiny sea urchin. The caterpillar will spend it’s early instars hiding in a curled up dead leaf from which it will periodically venture out to feed. The larval foodplants of duryodana are unknown, but in common with other Neptis species it will probably be polyphagous. The chrysalis will resemble a withered leaf, and will be suspended by the cremaster from a leaf or stem on or near the foodplant.
Adult behaviour
Like all Neptis species, this butterfly is best appreciated when on the wing, as it sails gently, riding on thermals, with periods of gliding punctuated by occasional sharp wing beats. The Malay Sailor flies with meticulous precision, gliding in circles as it weaves its way in and out through the foliage and branches.
Both sexes periodically alight to bask on the foliage of trees and bushes, or on the ground. Males sometimes imbibe moisture from damp ground, but like the females they are more often seen nectaring at flowers.