Diagnosis. The facies is similar to that of robustalis above but the species is much smaller. The antemedial and postmedial fasciae are similarly crenate, and the discal spots are also conspicuous. The male antennae have a node at one third, and the legs have tibial hair-pencils, but not the extreme development of that on the foreleg seen in robustalis. The species also resembles S. phaedrusalis Walker (p. 121) which is smaller and only known from females. In phaedrusalis, the forewing has a distinct angle subcostally, with the section running from this angle to the costa being straight; the underside is a more yellowish buff with the fasciation finely defined rather than somewhat diffuse. The male genitalia of discosticta are distinguished by the bifid apex to the valve (see also note below). The female genitalia have a very much longer ductus bursae than those of phaedrusalis.
Taxonomic note. The valve apex in Bornean material is somewhat narrower than in a specimen from the type locality of Sri Lanka, with the points less splayed. The aedeagus apex and vesica of the latter are generally more finely and evenly scobinate, though larger spines are associated with the base of the distal diverticulum in both.
Geographical range. Sri Lanka, Sundaland.
Habitat preference. All male specimens have been taken in highly disturbed, cultivated or inhabited areas of the lowlands. Females appear to be much commoner, with records from both primary and disturbed or logged forest in the lowlands, with a few taken in the lower montane zone to as high as 1000m.
