Non-consumptive effects on an ephemeral resource between an intraguild predator, Chrysomya rufifacies (Diptera: Calliphoridae), and its prey Cochliomyia macellaria (Diptera: Calliphoridae)

Non-consumptive effects (NCE) can have large behavioral costs to prey. Chrysomya rufifacies  (Macquart) is an introduced blow fly thought to be responsible for the eradication of native blow flies in South America. Cochliomyia macellaria (Fabricius) is a native blow fly to North America and often whose larvae are found on carrion interacting with Ch. rufifacies larvae. This study examined the NCE of Ch. rufifacies on C. macellaria larval growth. Larvae of C. macellaria, in each instar, were reared under laboratory conditions with or without the presence of predator cues (larval predator wash, NCE treatment). Rate of development was not significantly different (P > 0.05) between treatments and controls (deionized water) for any stage or overall development time. However, size (length or weight) from initial treatment time to pupariation was statistically different from controls. Much like the water flea, Daphnia Müller (Cladocera: Daphniidae), that respond in similar fashion to predatory cues they encounter, the physiological shift could assist C. macellaria in avoiding predation by Ch. rufifacies. These data are important for understanding the ability of C. macellaria to persist in the presence of a dominant predator. Additionally, these data are important in forensic entomology as these two flies often are encountered on remains in death investigations and thus used for calculating time of colonization or the minimum postmortem interval (mPMI). The presence of Ch. rufifacies may affect C. macellaria size and lead to reduced accuracy in mPMI estimates.  Accounting for this phenotypic variation could allow for more precise mPMI estimates.