About Sideridis rivularis Fabricius, 1775
Sideridis rivularis (Fabricius, 1775) has a wingspan of 27–30 mm, and its forewings measure 14–16 mm in length. The forewings are brownish fuscous with a violet sheen, and the lines are double. The claviform stigma is large and black, while the orbicular and reniform markings are grey with yellowish or whitish outlines; they are conversely oblique and contiguous along the median vein. The veins are dark, outlined with grey. The submarginal line is yellowish or white and dentate. The hindwings are brownish fuscous, darker in females. The aberration ab. behenis Frr. has a pale outer half of the forewing costa. S. mandarina Leech, which is now recognized as a separate species, occurs in Japan and China. It is rather larger and darker, with slightly less distinct markings as a result.
