Forensic entomology is a growing field within the Caribbean, but lacks practical application. There remains room for further growth inclusive of primary baseline information, such as determining the identity of flies of forensic importance on the various Caribbean islands. Descriptions of morphology and biology of immature stages of some flies are also lacking, especially for the family Sarcophagidae. Described here is the morphology of the third larval stage of two species of Sarcophagidae of forensic importance, Peckia (Peckia) chrysostoma (Wiedemann, 1830) and Blaesoxipha (Gigantotheca) plinthopyga (Wiedemann, 1830). The two species were found to colonise and breed in decomposing pig meat. Specimens collected were reared and dissected using light microscopy. Key larval features are illustrated for use in identification, as an alternative or addition to adult morphology. Structures described include the anterior and posterior spiracle, anal segment, and cephalopharyngeal skeleton. Both species are considered to be of forensic importance and have been shown to colonise human corpses in a review of the literature.