The correct identification of forensically important arthropods for post-mortem interval estimation is crucial, as the rate of larval development can vary substantially between species. The identification of forensically important blowflies of the genus Chrysomya (Diptera: Calliphoridae) may be hampered by their close morphological similarities, especially as immatures. The aim of this study was to establish whether genetically closely related blowfly species would share similar developmental profiles. This could permit the application of developmental data to a number of closely related species, including those for which thermodevelopmental studies are lacking. If Australian Chrysomya were found to share developmental profiles, identification of the blowfly specimen to a level beyond genus may not be necessary, or at least it may not be necessary to distinguish morphologically similar sister species. The three Chrysomya species studied were collected from the same geographical location (Cairns, Australia), reducing the effects of acclimation and population-level genetic variation. The experimental conditions in this study were virtually identical, which enabled direct comparisons to be made among the species. Blowfly larval lengths were obtained for 24-hourly intervals at constant temperatures of 25, 30, and 35 degrees C. The thermal preferences of newly-hatched feeding larvae were determined by their positions on a temperature gradient apparatus. This study established that all three species investigated differed significantly in their developmental profiles, despite the genetic closeness of the sister species Chrysomya megacephala (Fabricius) and Chrysomya saffranea (Bigot). Because of this, genetic distance was not considered to be a useful factor for predicting thermodevelopment profiles of closely related species within a genus, and highlights the necessity for correct species identification.