Eurema hecabe, the common grass yellow, is a small pierid butterfly species found in Asia, Africa and Australia. They are found flying close to the ground and are found in open grass and scrub habitats. It is simply known as "the grass yellow" in parts of its range; the general term otherwise refers to the entire genus Eurema. Description The common grass yellow exhibits seasonal polyphenism. The lepidopteran has a darker summer morph, triggered by a long day exceeding 13 hours in duration, while the shorter diurnal period of 12 hours or less induces a fairer morph in the post-monsoon period. Male Upperside (dorsal surface): yellow, variable in tint from sulphur to rich lemon yellow according to season and locality. Forewing: apex and termen deep black, this colour continued narrowly along the costal margin to base of wing, near which it often becomes diffuse; the inner margin of the black area from costa to vein 4 very oblique and irregular, between veins 2 and 4 excavate on the inner side, this excavation outwardly rounded between the veins and inwardly toothed on vein 3; below vein 2 the black area is suddenly dilated into a square spot which occupies the whole of the tornal angle; the inner margin of this dilatation is variable, in the typical form slightly concave. Hindwing: terminal margin with a narrow black band which is attenuated anteriorly and posteriorly; dorsal margin broadly paler than the ground colour. The region of dorsal surface that appears visibly yellow to humans also reflects brightly in the ultraviolet (320-400 nm) owing to the presence of multilayer cuticular nanostructures. Underside (ventral surface): yellow, generally a slightly paler shade than that of the upperside, with the following reddish-brown markings. Forewing: two small spots or specks in basal half of cell and a reniform (kidney-shaped) spot or ring on the discocellulars. Hindwing: a slightly curved subbasal series of three small spots, an irregular slender ring or spot on the discocellulars, followed by a highly irregular, curved, transverse, discal series of spots or specks, some or all of which are often obsolescent. On both the forewings and hindwings, the veins that attain the costal and terminal margins end in minute reddish-brown specks. Antenna are greyish yellow, the club black; head, thorax and abdomen are yellow, shaded with fuscous scales; beneath: the palpi, thorax and abdomen are yellowish white. The sex-mark seen from above appears as