The velvet black and blue males of this species are in strong contrast to the mottled brown females (known as sexual dichromatism). Both sexes are perchers, ususally with wings splayed. The females of a closely related species have been observed to have a fascinating way of determining as to whether a targeted foodplant is worth laying their eggs on. They have puncturing spines on their 'feet' and use them to burst surface plant cells and 'taste' them to assess palatability. The Horsfield's Baron has many subspecies reflecting its wide range from Thailand, China, Philippines to Malaysia, Borneo and Indonesia