Abstract
Larval P. pugio differ from larval P. vulgaris in the presence of chromatophores on pleonic sternite 2 in the former, but not in the latter species. Variation in the frequency of molting and the rate of development of larvae reared in the laboratory results in from 7 to 11 or more larval intermolts between hatching and metamorphosis. The sequence of events during development is the same in both species and does not vary with the tempo. The external morphology of individual larvae is a function of the rate of development and the frequency of molting and is related to total length, but is not an index of age or previous molting history.