Decomposition and arthropod succession on above ground pig carrion in rural Manitoba

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Gill, Ginger Julia
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This study was conducted to determine the succession of necrophilous insects on sun- and shade-exposed pig carrion. Twenty-two, seventy kilogram, clothed, fresh domestic pig carcasses (Sus scrofa L.) were monitored throughout decomposition in three rural areas in Manitoba during trials beginning in spring, summer and fall. A minimum of 13 arthropod orders, 61 families and 95 species collected manually and in pitfall traps over the duration of the study were identified. From this information, the arrival times and duration of stay were recorded for some of the most numerous species: Calliphora vicina Robineau-Desvoidy, Calliphora vomitoria (Linnaeus), Cynomya cadaverina (Robineau-Desvoidy), Lucilia illustris (Meigen), Phormia regina (Meigen) and Protophormia terraenovae (Roboneau-Desvoidy) (Calliphoridae); Prochyliza xanthostoma Walker, Stearibia nigriceps (Meigen) (Piophilidae); Necrodes surinamensis (Fabricius) and Oiceoptoma noveboracensis (Forster) (Silphidae); Creophilus maxillosus (Linnaeus) and Ontholestes cingulatus (Gravenhorst) (Staphylinidae); Necrobia rufipes (DeGeer) and Necrobia violacea (Linnaeus) (Cleridae); Glischrochilus quadrisignatus (Say) and Nitidula ziczac Say (Nitidulidae); Dermestes ater DeGeer, Dermestes fasciatus LeConte, Dermestes lardarius Linnaeus (Dermestidae); Trox unistriatus Beauvois (Trogidae) Geotrupes semiopacus Jekel (Geotrupidae) over the entire decay process. The Calliphoridae predominated in the carcasses during the fresh, bloat and decay stages of decomposition; predators such as the Staphylinidae and some Silphidae arrived in this sequence to feed on these species; as decay progressed, species of Silphidae, Piophilidae, Cleridae, Nitidulidae and Dermestidae, colonized the carcasses. There was no difference in the arthropod community collected from sun- and shade- exposed pig carrion; however, there were differences in species composition among the three rural areas. Calliphora vicina was present exclusively on sun-exposed carrion during the summer trial and on shade-exposed carrion in the spring trial; Calliphora vomitoria was collected solely during the fall trial; C cadaverina was found only during the spring trial. Phormia regina was the predominant calliphorid species and was pressent in sun and shade-exposed carrion in all three trials; L. illustris and P. terraenovae also occurred in all three areas. Ambient air temperature had no observed effect on maggot mass. temperature, however, during the summer trial, development time for P. regina was faster in sun-exposed carrion. Decomposition and insect colonization were monitored for more than 11 months for the spring trial, 14 months for the summer trial and 12 months for the fall trial. The fresh, bloat, decay and advanced decay stages of decomposition were obvious; however, a discrete stage beyond the advanced decay stage was not apparent. This study provides baseline information on the necrophilous fauna for estimating postmortem interval in cases of human death in Manitoba.