The developmental stages and castes of two sympatric subterranean termites, Macro-termes gilvus (Hagen) and Macrotermes carbonarius (Hagen) (Blattodea: Termitidae) were studied and biometric descriptors of each caste were developed for the identification of both species. Biometric descriptors revealed five well-defined groups of larval castes. After sex determination, three larval instars were detected in the development of minor and major worker castes. The first larval instars consist of both males and females which are homogenous in size. Size sexual dimorphism, in which females are smaller than males, occurs in the second larval instars, third larval instars, and worker castes. Minor and major soldiers are female sterile castes. Pictorial evidence of the fourth larval instar of M. carbonarius is presented herein; the individuals closely resemble minor workers but are poorly pigmented and have a distended abdomen, future presoldier-like mandibles, and a meso- and metanotum. In reproductive caste development, nymphs (derived from the first larval instars) undergo five moults from first to fifth instars before becoming winged termites.