Complete larval development and first crab stages of the sesarmid crabs Armases roberti (H. Milne Edwards, 1853) and A. ricordi (H. Milne Edwards, 1853) from Jamaica were obtained from laboratory culture. All larval stages (four zoeal stages and the megalopa) and the first juvenile crab stage of A. roberti are described and illustrated in detail for the first time, and a previous description of the larvae and the first crab of A. ricordi is revised and complemented. In addition, the first zoeal stage of A. americanum (de Saussure, 1858) is described for the first time. The morphological characters of the larvae of the three sesarmid species are compared with those of other known larvae of the genera Armases Abele, 1992 and Aratus H. Milne Edwards, 1837. Several characters are described for the first time for zoeal stages of the genus Armases, especially minute spines on the telson and the setation of the coxa of the first maxilliped. Minor differences were also observed between the earlier and the present description of A. ricordi, and additional characters are included here, in particular the cephalothoracic setation. The zoeal morphologies of A. roberti and A. ricordi only show minor meristic and morphometric differences, but the megalopae of both species can easily be distinguished by the setation of the sternum.