The carrion beetle Oxelytrum discicolle (Brullé, 1840) has forensic importance in the Neotropical region. The age of their larvae can provide important information to estimate the minimum postmortem interval of the corpse. This study was designed to determine the larval stages of this species, using three morphological measurements, as follows: distance between dorsal stemmata, pronotal width, and total body length. Three instars were identified. Distance between dorsal stemmata and pronotal width were good discriminating variables to determine instars, whereas total length was widely variable. For each instar, intervals of three morphological measures are given.