Applied studies of some Southern African blowflies (Diptera: Calliphoridae) of forensic importance
- Authors: Lunt, Nicola
- Date: 2003
- Subjects: Diptera -- South Africa , Blowflies -- South Africa , Forensic entomology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5803 , http://hdl.handle.net/10962/d1006202 , Diptera -- South Africa , Blowflies -- South Africa , Forensic entomology
- Description: Three major aspects of blowfly (Diptera: Calliphoridae) research were the focus of this study. Firstly, the phylogenetic relationships of 40 oestroid species from a variety of geographical localities were investigated using Cytochrome Oxidase b subunit I (COl) gene sequences. Maximum parsimony (MP) and Jukes-Cantor neighbor-joining (NJ) analyses both extracted a paraphyletic Calliphoridae, with the Calliphorinae-Luciliinae clade being sister to the Sarcophagidae. Short branch lengths within Chrysomya indicate a recent rapid radiation of this genus. Phormia and Protophormia either formed a sister clade to Chrysomya, or were embedded in this genus. Tree topologies were comparable between MP and NJ trees, but the positions of some genera were ambiguous. Secondly, developmental parameters and behaviour were investigated for four southern African species of forensically important blowflies viz. Chrysomya chloropyga, C. putoria, C. megacephala and Lucilia sericata, and ad hoc observations were made for Calliphora croceipalpis, Chrysomya marginalis and the predatory C. albiceps. Choice of oviposition substrate differed between species, mirroring substrate preferences in the field. Sexual dimorphism and dwarfism within a cohort complicated ageing maggots using size, but the use of developmental events (e.g. ecdysis) allowed ages to be determined unambiguously. Separate species status was supported for the previously synonymised C. chloropyga and C. putoria, by differences in maggot behaviour, larval growth rates and temperature optima. The proportion of total development time assigned to each larval instar and pupariation was variable among temperatures, but similar between congeneric species. Thirdly, since a negative linear relationship was found to occur between the developmental constant (K) and developmental zero (D₀) for both Calliphoridae and Sarcophagidae, the potential for predicting physiological parameters of unstudied taxa was investigated. Species and genera of Palaearctic origin generally had high K's and low D₀'s, and the reverse was true for the tropical taxa. It was found that both K and D₀ can be estimated for "unknown" taxa using the Felsenstein's Independent Contrasts (FIC) method of PDTree (Garland et al. 200 I), provided that branch lengths are relatively short and the phylogenetic position of the estimated taxon is unambiguous.
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- Date Issued: 2003
Spatial and temporal occurrence of forensically important South African blowflies (Diptera: Calliphorida)
- Authors: Williams, Kirstin Alexa
- Date: 2003
- Subjects: Blowflies -- South Africa , Forensic entomology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5617 , http://hdl.handle.net/10962/d1003217 , Blowflies -- South Africa , Forensic entomology
- Description: Forensic entomology is an emergjng field in South Africa. Little is known about South African blowflies and factors that affect their use in a forensic context. This work provides a review and synthesis of previous work in South Africa and supplements some of the background and basic knowledge required for forensic entomology in South Africa. The seasonal occurrence of eight forensicaIIy important blowfly species was quantified by fortnightly trapping in Grahamstown, South Africa. The spatial distribution of each species was related to seasonal occurrence and habitat preference. Seasonal distributions of blowflies in carcasses in South Africa were obtained from the literature and compared to the seasonal trapping. By mapping South African locality records of forensicaIIy important blowflies and analyzing these records in a modified Principal Components Analysis of climatic data, the potential geographic distributions of each fly species was modeIIed. Most species were widespread, but Calliphora croceipalpis, Jaennicke, 1867, was found in cold places. This information is important for determining where certain species are likely to occur in forensic investigations. Nocturnal oviposition was examined in both field and laboratory experiments. Lucilia species could oviposit nocturnaIIy in the field, while Lucilia species, Chrysomya chloropyga, (Weidemann, 1818) and C. putoria (Weidemann, 1830) could oviposit nocturnaIIy in the laboratory. These findings are important factors in affecting the precision of estimates of a post mortem interval (PM!) by up to 12 hours. The thermophysiological ranges of four species of adult blowflies were determined by measuring onset temperatures of four significant behaviours: onset of neural activity; onset of coordinated movement; shade-seeking and death. There was a sexual size dimorphism in Lucilia species, Chrysomya chloropyga and Calliphora croceipalpis with females being larger than males. Chrysomya megacephala (Fabricius, 1794) had an unexpectedly high death threshold, while Calliphora croceipalpis had the lowest death threshold of the flies tested. These points were related to the seasonal and geographic occurrence of each species, to nocturnal activity and placed in a forensic context.
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- Date Issued: 2003