Background/Question/Methods Within ecology, there are many systems where resource limitation acts as a driving force for competition and coexistence. Carrion represents an ephemeral resource where a unique insect community develops, exhibiting distinct changes in community composition over spatial and temporal scales. Within the carrion insect community, Calliphorids represent the primary resource colonizers responsible for the rapid removal of biomass during decomposition, where blow fly species commonly experience high levels of competition due to the nature of the resource and the number of larvae present. The effects of arrival order were investigated using three blow fly species: Phormia regina (Meigen), Chrysomya rufifacies (Macquart) and Lucilia sericata (Meigen). A total of 400 first instar larvae were transferred to fetal pig carcasses (Sus scrofa (Linnaeus)), where the arrival sequence of each species varied. A total of 5 treatment conditions were used for each experimental design which consisted of L. sericata first, L. sericata second, L. sericata and P.regina/C. rufifacies at the same time, and P. regina/C. rufifacies/L. sericata alone. Larval, pupal and emergent adult mortality was measured. Emergent adult fitness was measured through the use of the following fitness variables: hind tibia length, thorax length and wing length. Results/Conclusions Results indicate that L. sericata experiences a reduction in emergent adult fitness in the presence of P. regina and C. rufifacies. Alternately, P. regina and C. rufifacies experiences lower larval/pupal mortality, however, no reduction in adult fitness in the presence of L. sericata. Thus, L. sericata may act as a facilitator to promote the survival and fitness potential of P. regina and C. rufifacies. The different effects of competition on mortality and fitness demonstrated by these two blow fly species suggest that alternative strategies for survival can be adopted to allow for coexistence within the Calliphorid family.