Browsing by Author "Drijfhout, Falko P."
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Item Open Access Adult fly age estimations using cuticular hydrocarbons and Artificial Neural Networks in forensically important Calliphoridae species(Elsevier, 2017-10-08) Moore, Hannah E.; Butcher, John B.; Day, Charles R.; Drijfhout, Falko P.Blowflies (Diptera: Calliphoridae) are forensically important as they are known to be one of the first to colonise human remains. The larval stage is typically used to assist a forensic entomologists with adult flies rarely used as they are difficult to age because they remain morphologically similar once they have gone through the initial transformation upon hatching. However, being able to age them is of interest and importance within the field. This study examined the cuticular hydrocarbons (CHC) of Diptera: Calliphoridae species Lucilia sericata, Calliphora vicina and Calliphora vomitoria. The CHSs were extracted from the cuticles of adult flies and analysed using Gas Chromatography-Mass Spectrometry (GC-MS). The chemical profiles were examined for the two Calliphora species at intervals of day 1, 5, 10, 20 and 30 and up to day 10 for L. sericata. The results show significant chemical changes occurring between the immature and mature adult flies over the extraction period examined in this study. With the aid of a Principal Component Analysis (PCA) and Artificial Neural Networks (ANN), samples were seen to cluster, allowing for the age to be established within the aforementioned time frames. The use of ANNs allowed for the automatic classification of novel samples with very good performance. This was a proof of concept study, which developed a method allowing to age post-emergence adults by using their chemical profilesItem Open Access Cuticular hydrocarbons for identifying Sarcophagidae (Diptera)(Nature Publishing Group, 2021-04-08) Moore, Hannah E.; Hall, Martin J. R.; Drijfhout, Falko P.; Cody, Robert B.; Whitmore, DanielThe composition and quantity of insect cuticular hydrocarbons (CHCs) can be species-specific as well as sexually dimorphic within species. CHC analysis has been previously used for identification and ageing purposes for several insect orders including true flies (Diptera). Here, we analysed the CHC chemical profiles of adult males and females of eleven species of flesh flies belonging to the genus Sarcophaga Meigen (Sarcophagidae), namely Sarcophaga africa (Wiedemann), S. agnata Rondani, S. argyrostoma Robineau-Desvoidy, S. carnaria (Linnaeus), S. crassipalpis Macquart, S. melanura Meigen, S. pumila Meigen, S. teretirostris Pandellé, S. subvicina Rohdendorf, S. vagans Meigen and S. variegata (Scopoli). Cuticular hydrocarbons extracted from pinned specimens from the collections of the Natural History Museum, London using a customised extraction technique were analysed using Gas Chromatography–Mass Spectrometry. Time of preservation prior to extraction ranged between a few weeks to over one hundred years. CHC profiles (1) allowed reliable identification of a large majority of specimens, (2) differed between males and females of the same species, (3) reliably associated males and females of the same species, provided sufficient replicates (up to 10) of each sex were analysed, and (4) identified specimens preserved for up to over one hundred years prior to extraction.Item Open Access Cuticular hydrocarbons for the identification and geographic assignment of empty puparia of forensically important flies(Springer, 2022-02-26) Moore, Hannah; Lutz, Lena; Bernhardt, Victoria; Drijfhout, Falko P.; Cody, Robert B.; Amendt, JensResearch in social insects has shown that hydrocarbons on their cuticle are species-specific. This has also been proven for Diptera and is a promising tool for identifying important fly taxa in Forensic Entomology. Sometimes the empty puparia, in which the metamorphosis to the adult fly has taken place, can be the most useful entomological evidence at the crime scene. However, so far, they are used with little profit in criminal investigations due to the difficulties of reliably discriminate among different species. We analysed the CHC chemical profiles of empty puparia from seven forensically important blow flies Calliphora vicina, Chrysomya albiceps, Lucilia caesar, Lucilia sericata, Lucilia silvarum, Protophormia terraenovae, Phormia regina and the flesh fly Sarcophaga caerulescens. The aim was to use their profiles for identification but also investigate geographical differences by comparing profiles of the same species (here: C. vicina and L. sericata) from different regions. The cuticular hydrocarbons were extracted with hexane and analysed using gas chromatography-mass spectrometry. Our results reveal distinguishing differences within the cuticular hydrocarbon profiles allowing for identification of all analysed species. There were also differences shown in the profiles of C. vicina from Germany, Spain, Norway and England, indicating that geographical locations can be determined from this chemical analysis. Differences in L. sericata, sampled from England and two locations in Germany, were less pronounced, but there was even some indication that it may be possible to distinguish populations within Germany that are about 70 km apart from one another.Item Open Access Geographical variation of cuticular hydrocarbon profiles of adult flies and empty puparia amongst three populations of Calliphora vicina (Diptera: Calliphoridae)(Oxford University Press, 2022-11-14) Kula, Canan; Amendt, Jens; Drijfhout, Falko P.; Moore, Hannah E.Blowflies (Diptera: Calliphoridae) are of great importance in forensic entomology and in determining the minimum post-mortem interval, as they may be the first group of insects to colonise decomposing remains. Reliable species identification is an essential prerequisite. Classically, morphological characters or DNA sequences are used for this purpose. However, depending on the species and the condition of the specimen, this can be difficult, e.g. in the case of empty fly puparia. Recent studies have shown that cuticular hydrocarbon (CHC) profiles are species-specific in necrophagous taxa and represent another promising tool for identification. However, the population-specific variability of these substances as a function of e.g. local climatic parameters has not yet been sufficiently investigated. The aim of this study was to determine the geographical variation of CHC profiles of the blowfly Calliphora vicina depending on different countries of origin. Flies were reared in the UK, Germany and Turkey in common garden experiments under ambient conditions. CHC profiles of the resulting adult flies and their empty puparia were analysed using gas chromatography-mass spectrometry. Data were visualised by principal component analysis and clustered by population. The populations of the UK and Germany, both having similar climates and being geographically close to each other, showed greater similarities in CHC profiles. However, the CHC profile of the Turkish population, whose climate is significantly different from the other two populations, was very different. Our study confirms the high potential of CHC analysis in forensic entomology but highlights the need to investigate geographical variability in chemical profiles.