Unveiling one of the rarest 'butterflies' ever (Lepidoptera: Hesperiidae, Noctuidae).

Many insect species named by the Danish entomologist J.C. Fabricius remain enigmatic due to loss of the original type specimens, sketchy descriptions and lack of illustrations, but even some well-illustrated taxa remain unrecognized. This is the case for Hesperia busiris, a 'butterfly' illustrated by W.J. Jones, the identity of which has puzzled experts for 225 years. Here we argue that the description and illustrations of this species are a perfect fit to a colourful moth later described by F. Walker as Eusemia contigua. Furthermore, we present evidence that Walker unwittingly based his name on the same specimen as Fabricius, and that this is the only known example of this species. An extraordinary sequence of misconceptions led the geographic origin of this specimen to become thoroughly confused, so that it is currently unknown where on Earth this species may occur (although a substantial body of evidence points to West Africa) and if it is even still extant.