The larval development of the spider crab Menaethius monoceros (Latreille, 1825) (Crustacea: Decapoda: Brachyura: Majoidea: Epialtinae) is described and illustrated from laboratory-reared larvae. The development consisted of two zoeal stages and one megalopa, following the typical pattern in Majoidea. The duration of the first zoeal stage was 4-11 days, the second zoea appearing 5-12 days and the megalopa 10-18 days after hatching. Both zoeal stages of Menaethius monoceros have a distinct setation on the distal segment of the endopod of maxilliped II. In the megalopa only the setation of the exopod of the antennule is diagnostic among Epialtinae. Comparative analysis revealed that some of the previous descriptions are probably not those of Menaethius monoceros. Based on existing limited information no single morphological feature, or set of features, is apparent that characterizes epialtine larvae.