| Abstract | Research was undertaken to explore the succession of insects on a decomposing body and to identify the semiochemicals responsible in initially attracting blowflies, specifically
Calliphora vomitoria, to the body. Five adult pigs were used for studies of insect succession and decomposition. Different
species of insects are attracted to a decomposing body at different stages of decomposition. This was evident throughout all the experiments with blowflies C. vicina
and C. vomitoria being the first to arrive on the experimental pigs and colonise the body. Muscidae and Lucilia sp. closely followed. Silphidae and Staphylinidae beetles, adults and immature stages, were present early during decomposition; however, during the last stage of decomposition Cleridae, Histeridae, and Dermestidae beetles were much more numerous. Warmer temperatures presented increased insect activity and rate of tissue removal, while rain triggered a mass larval migration from the body. Maggot masses greatly elevated the temperature inside a corpse. While the presence of adults of a single species on the body could not alone be used to identify a specific point in insect . succession, their presence with a particular combination of other insect species, their abundance, and that of their offspring all helped define a succession pattern. Combined gas chromatography (GC) and electroantennogram (EAG) experiments identified four volatile chemicals recovered from the decomposing pigs which elicited a receptor response from C. vomitoria: dimethyl disulfide, dimethyl trisulfide, dimethyl tetrasulfide, and a compound of unknown structure (KI 881-885). Dose response experiments demonstrated that dimethyl trisulfide and dimethyl tetrasulfide elicited the greatest receptor responses. A positive correlation was found between the concentration of
these compounds and the number of flies on the pig carcass. The chemical composition and concentration of the compounds associated with decay, in particular the EAG-active compounds, varied between the different stages of decomposition. None of the EAGactive compounds caught a significantly greater number of blowflies than unbaited traps
when water trap and sticky trap experiments were conducted. The positive control, a mixture of sodium sulfide and liver, also failed to capture significantly more blowflies than the controls. While fewer than expected blowflies were captured during these experiments, a greater insight into suitable trapping methods and bait composition was gained. |
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