Byasa alcinous can be found in the Asian part of the Palaearctic realm and parts of the Indomalayan realm, from Bhutan  and eastern China to the southern Ussuri region, Korea and Japan.
   Their preferred habitat is mixed broad leaf forests.
   The color of their wings is black or dark brown.
   The hindwings have long tails and a chain of red spots at the edges.
   The thorax and the abdomen are mainly black on the dorsal side and the ventral side, with several black spots, while the other areas are red.
   Adults have 2 generations, and are on wing from May to August.