Doctoral Degrees (Zoology and Entomology)
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Browsing Doctoral Degrees (Zoology and Entomology) by Author "Brink, Sonja Lindsey"
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Item Open Access Key diagnostic characteristics of the developmental stages of forensically important calliphoridae and sarcophagidae in central South Africa(University of the Free State, 2011-12-15) Brink, Sonja Lindsey; Van der Linde, Theuns C. de K.; Basson, Linda; Van Wyk, Pieter W. J.English: The first insects attracted to a decomposing body are usually representatives of the Diptera, in particular members of the families Calliphoridae (blow flies) and Sarcophagidae (flesh flies). These flies will deposit their eggs (or often larvae in the case of sarcophagids) on the body, within a few hours after death, depending on environmental conditions. The immature stages will complete their developmental cycle on and around the body. As a consequence, these insects are of great importance in forensic entomology; the main area of application being the determination of the postmortem interval (PMI). One of the key pieces of information needed to calculate the PMI is the correct species identification of the immature stages. The aim of this study was to provide diagnostic descriptions for the immature stages of forensically important calliphorids and sarcophagids in central South Africa. Forensically important calliphorids prevalent in this region are Lucilia cuprina (Wiedemann), Lucilia sericata (Meigen), Chrysomya chloropyga (Wiedemann), Chrysomya marginalis (Wiedemann), Chrysomya albiceps (Wiedemann) and Calliphora vicina Robineau-Desvoidy. The sarcophagid prevalent in the region is Sarcophaga cruentata Meigen. A range of characteristics was evaluated by means of light and scanning electron microscopy and the most pertinent of these were identified for diagnostic purposes. The eggs were evaluated in terms of nine characteristics; six of which were of no diagnostic use, while three could be used to identify some of the species. The eggs of C. chloropyga and C. albiceps were indistinguishable from each other. Twelve features were identified for their possible diagnostic value in larvae. In first instar larvae five of these characteristics were of no diagnostic value, while six were useful to identify some of the species. All species could, however, be identified with the aid of the cephalopharyngeal skeleton. For second instar larvae, four of the characteristics were of no diagnostic use, but seven were useful to identify some of the species. All the species could be identified using the cephalopharyngeal skeleton. In the third instar larvae four characteristics were of no diagnostic use, but by using three other characteristics some of the species could be identified. All the species could be identified by means of five morphological characteristics (labrum, cephalopharyngeal skeleton, posterior spiracles, spiracular plate and anal area). Seven characteristics were identified for their possible diagnostic values in puparia. Five of these characteristics were useful to identify some of the species, but all the species could be identified with the aid of two of the characteristics (frontal field and bubble membrane). The ultimate aim of the study was to construct keys for use during the identification of specimens found at the crime scene. The keys that were constructed not only mapped out the pertinent diagnostic characteristics, but also considered what characteristics could be combined when a specimen was viewed from a specific angle. Since specimens often reach the forensic laboratory in less than optimal condition, it is essential that a wide range of characteristics and keys be available during identification. This will also enable the forensic entomologist to give priority to specimen preparation and the method of observation when rapid analysis is needed or where very few good specimens are available for identification. With these tools (descriptive diagnostic characteristics and keys) the identification of immature stages of calliphorids and sarcophagids found at the crime scene should be an uncomplicated exercise.