Abstract

Carrion flies, particularly blow flies (Diptera: Calliphoridae) and flesh flies (Diptera: Sarcophagidae), play a vital role in the cycling of organic material by aiding in the decomposition of vertebrate cadavers in terrestrial ecosystems. Because of this close association with dead bodies, these flies also serve as the primary indicators of the postmortem interval for forensic entomologists based on the rapid nature of fly colonization. I addressed some of the assumptions made with regard to the colonization of terrestrial cadavers by carrion flies. This starting point was ideal because the whole of insect-driven decomposition begins with the colonization of the cadaver, usually by flies.

By first conducting experiments on the potential for blow flies to produce multiple generations on single cadavers, I was able to demonstrate through a choice/no choice scenario that blow flies do not in fact produce a second generation on carrion. This has confirmed assumptions in the literature which had previously not been tested. As a follow-up to this study, I examined the effects of decomposition on vitellogenic protein sources for blow flies to determine whether or not flies visiting decomposed bodies are indeed gaining dietary protein as has been assumed. My data show that flies successfully complete vitellogenesis on aged carrion at the same rate as they do on fresh liver.

Finally, I tested the assumption that flies do not colonize bodies at night, an assumption that has been tested several times before by various authors using inappropriate experimental procedures. By killing pigs (23-32 kg each) after dark, and placing them in field conditions of varying light intensities, I was unable to show any signs of carrion fly colonization. This reinforces the assumption that flies do not colonize bodies after dark, and indicates that the potential for nocturnal colonization of a body by flies has been overstated by some authors.