The cheese (or ham) skipper, Piophila casei (Linnaeus), belongs to the family Piophilidae and is a detritivore species that feeds on decaying organic matter. Its larvae are commonly found on high-protein substrates (including carcasses), with a life cycle that is strongly influenced by environmental temperature and food nature. In this study, we investigated development time and larval length of P. casei reared on Parma ham PDO (Protected Designation of Origin) at five constant temperatures (20, 22, 24, 26, 28 °C). We calculated the accumulated degree days (ADD) and constructed isomegalen- and isomorphen-diagrams to estimate the infestation time. The minimum development threshold (t_L) obtained by extrapolating the development rates measured between 20 °C and 28 °C was 9.91 °C, resulting in ADDs (oviposition–eclosion) of 216.9, 219.9, 220.7, 209.2, and 220.1 at 20, 22, 24, 26, and 28 °C, respectively.