The Sunset Morpho (Morpho hecuba) is a Neotropical butterfly and the largest species in the genus Morpho. Its wingspan can reach 20 centimetres (7.9 in), but is usually from 13–15 centimetres (5.1–5.9 in). "M. hecuba is the largest known Morpho and one may also call it the most interesting, on account of its habits, its susceptibility to climatic influences and its tendency to develop polychromatic forms in both sexes."