The puerulus of Panulirus guttatus is described and compared with that of P. argus , a sympatric species. Comparative morphological data show that the former has a more specialized form than the latter and hence is more recent in evolutionary terms. Features characterizing the puerulus of P. guttatus are its relatively large size, long spatulate antennae, and well developed sternal spines. The possible adaptive value of the long spatulate antennae for selection of specific substrata and/or navigation through inshore waters is discussed in relation to the ecology of the juvenile and adult phases. Pueruli of P. guttatus are not found in the surface collectors, resembling marine vegetation, used to monitor the influx of pueruli of P. argus into coastal waters on the Caribbean coast of Mexico. Moreover, small juveniles of P. guttatus are never found in the natural habitat of those of P. argus , and large juveniles and adults of P. guttatus seem restricted to the shallow coral reef habitat, in contrast to similar phases of P. argus , which occupy a vast array of habitats and depths throughout their benthic life. It is hypothesized that the pueruli of both species settle in different habitats, which would partly explain their sharing of the same geographic distribution.