Experiments were conducted to determine whether a specific larval substrate impacted immature development rates. Protophormia terraenovae was raised on beef organs and compared with whole carcasses (rat), to determine if discrepancies in development times were observed. The minimum development time on beef liver was the most consistent with the rat carcass but a significant difference between all substrates was found after the third instar. These differences can be explained by the differences found between heart and muscle and the other substrates. Often length of the larvae is used to estimate insect age and so Day 2 measuring of weight, length, and width of the pupae was undertaken. Significant differences were found for all parameters measured on each of the substrates. As a result, the use of these measurements should not be done for P. terraenovae due to conflicting rearing substrates. Significant differences within substrates were only found for weight of insects developing on heart and length of insects developing on muscle. There was no significant difference in survival from first instar to the adult stage on any of the substrates but personal observation suggested that mortality was higher in insects developing on the brain tissue.