The systematics of the Calappa lophos species group is clarified using morphological and molecular data. The phylogeny of some Indo-Pacific species of Calappa is discussed. Two species, C. quadrimaculata Takeda and Shikatani, 1990, and C. guerini (Brito-Capello, 1871), previously synonymised with C. lophos (Herbst, 1782), are shown to be valid species using morphological and molecular data. A new species in the group, C. acutispina, is described from Madagascar. The usefulness of Bayesian inference in elucidating the phylogenetic relationships of some of the species of Calappa based on partial cytochrome oxidase I (COI) sequences is examined.