Silphid larvae of three species of potential forensic importance were studied to verify total instar number, document instar size classes, and illustrate frequencies of instars through time. Larval material was collected at seven large vertebrate carcasses during spring 1999 in East Baton Rouge Parish, LA. A total of 534 Necrodes surinamensis (F.), 80 Oiceoptoma inaequale (F.), and 13 Necrophila americana (L.) larvae were evaluated using three morphological measurements. Three instars were identified for N. surinamensis and O. inaequale. The distance between dorsal stemmata was found to be a more reliable indicator of instar size than body length with results (in mm) as follows for N. surinamensis and O. inaequale, respectively: 1st (0.87–1.09), (0.95–1.08), 2nd (1.30–1.60), (1.28–1.51), and 3rd (1.78–2.07), (1.66–1.79).