Masters Degrees (Zoology and Entomology)
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Browsing Masters Degrees (Zoology and Entomology) by Author "Brink, Sonja L."
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Item Open Access Decomposition and arthropod succession on buried remains during winter and summer in central South Africa: forensic implications and predictive analyses(University of the Free State, 2016-01) Botham, Jason Lee; Brink, Sonja L.English: While burial is utilised by criminals as a means of disposing of a body, knowledge of the impact it has on arthropod succession and decomposition within South Africa is currently lacking. The study was conducted within a 24 hectare grassland field, located on the University of the Free State grounds. A total of seven pig carcasses (Sus scrofa Linnaeus) were utilised for each of the two seasonal trials, with six of them being buried in randomly spaced graves at depths of 60cm and one placed above-ground as a control. Each of the graves was excavated on predetermined days over each 60 day trial to minimise disturbance and evaluate the impact of differing time periods on decomposition and arthropod succession. After its initial excavation, grave one was excavated every third day until the conclusion of the trial to determine the impact of disturbance on buried remains. Decomposition and biomass loss progressed faster on buried carcasses compared to aboveground during the winter season. A faster rate of decomposition and biomass loss was seen for the above-ground carcass versus the below-ground carcass during the summer season, mainly due to heavy rainfall causing waterlogging of the graves. Between the two seasons, a higher decomposition and biomass loss rate was recorded on the summer buried carcasses compared to those buried in winter. Dipteran species were seen to dominate on the summer control carcass, while, during the winter trial, the coleopteran species, Dermestes maculatus De Geer (Dermestidae), was noted to extensively colonise and outcompete present dipteran individuals. With cold, dry climatic conditions leading to the winter control carcass undergoing a form of mummification, adult D. maculatus individuals were seen to congregate on the carcass and reproduce, leading to larval aggregation during the active decay stage. During the trials, only dipteran species were found to colonise the winter buried carcasses, whereas the summer buried carcasses were colonised by two dipteran species, a predatory coleopteran species and an Acari species. Of those species colonising the winter buried carcasses, two Phoridae species were found to be the most abundant, being identified as Megaselia scalaris (Loew) and Conicera tibialis Schmitz, and colonised the buried carcasses from day 21 onwards. Later occurring dipteran species in winter included Muscina stabulans (Fallén) and a species of the genus Leptocera Olivier. Summer buried carcasses saw initial colonisation occurring from day 21 by phorid M. scalaris and a coleopteran beetle species from the genus Aleochara Gravenhorst (Staphylinidae). Further colonisation of the summer buried carcasses was seen after 30 days, with sarcophagid pupae and the Acari species Sancassania mycophagus (Mégnin) being sampled from the buried carcasses. From the analyses of data gained from the two seasonal trials, predictions were made regarding the time frames of decomposition and arthropod succession applicable to buried carcasses within central South Africa. Concurrently, alternative methodologies for burial excavations and entomological evidence collection were suggested for investigators, to take into consideration during burial crime scene investigations within central South Africa.Item Open Access The identification of Diptera of the grave and their succession patterns during winter and summer in central South Africa, with reference to forensic applications(University of the Free State, 2016-01) Van der Merwe, Sylvia Shalomé; Brink, Sonja L.; Basson, LindaEnglish: Forensic entomology is a specialist branch of forensic sciences in which information about insects is used to draw certain conclusions when investigating medico-legal cases involving both humans and wildlife. The primary application of insects collected from a crime scene is to determine the Post-Mortem Interval (PMI). One of the principal cornerstones in the effective application of forensic entomology is the correct identification of species found at a crime scene. The estimation of PMI using succession and developmental data is dependent upon the specific species that were present on a cadaver. The aim of this study was to identify the members of the Diptera that are capable of colonising buried carrion within a Free State grassland area, as well as to compare below ground dipteran data with above ground dipteran succession patterns. The field experiments, conducted in order to determine what species of Diptera are capable of reaching buried carrion during winter and summer months, as well as to determine the succession patterns of Diptera on buried remains, were conducted on the west fields of the University of the Free State campus, in central South Africa. The area is characterised by dry mild winters and warmer summers, with occasional rainfall periods. A total of seven pigs (Sus scrofa Linnaeus 1758) were used during each season, which consisted of one above ground control carcass and six separate below ground carcasses buried at 60 cm. Below ground carcasses were left for predetermined periods of time and were excavated on separate occasions over each 120 day trial period to monitor dipteran occurrence, colonisation and dipteran interactions. Members of Diptera were found to colonise carcasses at 60 cm during both winter and summer trials. Higher dipteran species diversity was noted on the buried winter carcasses in comparison to the buried summer carcasses. Four species of Diptera, Megaselia scalaris (Loew 1866) (Phoridae), Conicera tibialis Schmitz 1925 (Phoridae), Muscina stabulans (Fallén 1817) (Muscidae) and Leptocera Olivier 1813 sp. (Sphaeroceridae) were seen to occur on winter carcasses, with first colonisation taking place from day 21 of the winter trial. Three species of the Diptera, M. scalaris, Leptocera sp., and Sarcophaga Meigen 1826, were seen to colonise buried summer carcasses, with first colonisation taking place from day 21 of the summer trial. Dipteran faunal composition on buried carcasses was noted to be different to that of Diptera on above ground carcasses during both the winter and the summer trials. Statistical analysis showed that there was a significant difference between above ground and below ground dipteran faunal similarity. Preservation experiments on immature Diptera of the grave for identification purposes showed that the standard preservation mediums used for insects of forensic importance, such as ethanol solution and formaldehyde solution, are not effective. Preservation of adult samples was successful in 70% ethanol solution. Breeding trials under laboratory conditions proved effective in breeding larval instars found on buried carcasses through to adulthood for identification. Due to the difficulty in preservation of immature individuals of Diptera of the grave, and the ease of breeding larvae of these dipteran species, identifications were done on adult specimens. Adult Diptera were described based on taxonomic criteria, including wing venation, setal hairs and the hypopygium of male phorid specimens, and a simplified identification key was successfully compiled using morphology of the adult Diptera of the grave.