The land crab Johngarthia planatus is an eastern tropical Pacific species with a known distribution from Mexico to Colombia. Complete larval development of the species is fully described and illustrated from laboratory-reared material. The five zoeal stages and the megalopa are compared with those of Gecarcinus lateralis lateralis from the Atlantic coast. Main differences for zoeal stages are observed in the carapace and telson lateral spines while minor differences are observed in the mouthparts setation. For the megalopa stage a difference in size of the third maxilliped exopod supports the separation of Johngarthia from Gecarcinus. A brief comparison of all known zoea I and megalopa stages of species of the Gecarcinidae is made, taking into account recent new descriptions.