Morphological variability among four species of Mycalesis in Sri Lanka that are difficult to discriminate due to their morphological similarity was investigated to identify characters that distinguish species more accurately. Using traditional morphometrics, 90 variables from the wing, forelegs and genitalia of M. perseus typhlus, M. mineus polydecta, M. subdita and M. rama were measured and analysed. A set of 19 characters of the wing, male genitalia and forelegs were identified to discriminate species. Results of the analysis showed that male specimens were discriminated with nine wing characters and five characters of genitalia. Females could be discriminated with three wing characters and two foreleg characters. Male specimens of M. p. typhlus and M. m. polydecta showed the greatest morphological differentiation, while females of M. subdita and M. rama were the most similar species. These results were used to improve the currently available identification key. Two instances of possible hybridisation were discovered: one between M. p. typhlus and M. m. polydecta and the other between M. p. typhlus and M. subdita. Hence, the species of Mycalesis, particularly M. p. typhlus, M. m. polydecta and M. subdita may not be strictly reproductively isolated in Sri Lanka. Preliminary comparisons of M. p. typhlus in Sri Lanka with M. p. tabitha of India indicated that the Sri Lankan subspecies is unlikely to be a synonym.

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1. The Pelopidas are a widely distributed genus of hesperiids ranging from the Afrotropical to Australasia. Based on traditional classification, four species are recorded from Sri Lanka: Pelopidas agna, P. mathias, P. subochracea and P. conjuncta. 2. The aim is to test the taxonomic hypotheses of the Sri Lankan Pelopidas as they are currently recognised based on morphology. We achieve this by analysing the phylogenetic relationships among the Pelopidas as well as between the Pelopidas and tribe Baorini both inside and outside of Sri Lanka. 3. We used DNA sequence data from the cytochrome oxidase c subunit I (COI) "barcode" region and two nuclear DNA regions, elongation factor 1-α (EF1-α) and wingless (Wgl) collected for Sri Lankan Pelopidas and combined with all available Pelopidas sequence data from public databases. 4. The reconstructed phylogeny showed that P. mathias, P. agna and P. conjuncta were not monophyletic. Additionally, P. agna in Sri Lanka may now be a hybrid population that retains the P. agna morphology but possesses the mitochondrial DNA of P. mathias (termed a 'ghost' population). Finally, two lineages of P. conjuncta were identified in Sri Lanka, appearing more closely related to other species of Pelopidas than to each other. 5. This study demonstrates the phylogenetic complexity within the Pelopidas and the uniqueness of the Sri Lankan Pelopidas that have not been previously appreciated. This new knowledge is important in planning conservation management and may also guide future work on the potential mechanisms of evolutionary diversification of island butterflies.