Larvae of a semiterrestrial grapsid crab that lives in mangrove swamps in Jamaica, Sesarma curacaoense, were reared in the laboratory from hatching through metamorphosis. The morphology of all larval stages and of the first juvenile crab instar is described in detail. It is compared with that in closely related coastal (S. reticulatum, S. rectum), freshwater (S. bidentatum), and terrestrial crab species (Metopaulias depressus, Geosesarma perracae). As in limnic and terrestrial relatives, the larval development of S. curacaoense is abbreviated, consisting of only two zoeal stages and a megalopa. The lack of a Zoea III stage as well as an exceptionally early appearance of advanced morphological features in the development of the maxilliped 3 and the pereiopods represent phylogenetically derived characters in S. curacaoense. However, in most of their morphological features (e.g. carapace spines, segmentation of the antennule, armature of the antennal exopod, and endopods of the maxillule and the maxilla), the larvae of S. curacaoense are similar to those of coastal rather than to freshwater and terrestrial species. In particular, they do not reveal significant reductions in spines or appendages. Most morphological differences between these species are striking in the zoeal stages, but decrease in the Megalopa or in the first juvenile crab stage. In conclusion, the larval development of S. curacaoense is intermediate between that of ancestral (coastal) and derived (terrestrial and freshwater) species. This corroborates the hypothesis that S. curacaoense is a close relative of the ancestral species, from which, in a process of adaptive radiation, a number of endemic Jamaican freshwater and terrestrial crabs have evolved.