Abstract
Cuticular hydrocarbons (CHC) have been successfully used in the field of forensic entomology for identifying and ageing forensically important blowfly species, primarily in the larval stages. However in older scenes where all other entomological evidence is no longer present, Calliphoridae puparial cases can often be all that remains and therefore being able to establish the age could give an indication of the PMI. This paper examined the CHCs present in the lipid wax layer of insects, to determine the age of the cases over a period of nine months. The two forensically important species examined were Calliphora vicina and Lucilia sericata. The hydrocarbons were chemically extracted and analysed using Gas Chromatography – Mass Spectrometry. Statistical analysis was then applied in the form of non-metric multidimensional scaling analysis (NMDS), permutational multivariate analysis of variance (PERMANOVA) and random forest models. This study was successful in determining age differences within the empty cases, which to date, has not been establish by any other technique.
Highlights
Forensic entomology can be used to estimate the minimum Post Mortem Interval (PMImin) when insects associated with a body are examined, and the identity and age is determined
Studies on forensically important blowflies have proven to show great potential but these investigations are mainly presenting cuticular changes over time in relation to larvae[4, 20, 21], with only two studies being published on trying to establish age related changes from the cuticular hydrocarbons[1, 2]. This is the first study to establish the age of empty puparial cases from two forensically important blowflies in Europe using CHCs analysed on Gas Chromatography-Mass Spectrometry (GC-MS), non-metric multidimensional scaling analysis (NMDS) and permutational multivariate analysis of variance (PERMANOVA)
This study presents preliminary results with the aim of ageing the empty puparial cases of two species of blowflies, Calliphora vicina and Lucilia sericata using their CHCs over a period of nine months
Summary
Forensic entomology can be used to estimate the minimum Post Mortem Interval (PMImin) when insects associated with a body are examined, and the identity and age is determined. CHCs are composed of long linear chains of hydrogen and carbon atoms with a chain length varying from C17 to C35 In insects, they are observed in their saturated and unsaturated form and can have one or more methyl groups www.nature.com/scientificreports/. Studies on forensically important blowflies have proven to show great potential but these investigations are mainly presenting cuticular changes over time in relation to larvae[4, 20, 21], with only two studies being published on trying to establish age related changes from the cuticular hydrocarbons[1, 2] This is the first study to establish the age of empty puparial cases from two forensically important blowflies in Europe using CHCs analysed on Gas Chromatography-Mass Spectrometry (GC-MS), non-metric multidimensional scaling analysis (NMDS) and permutational multivariate analysis of variance (PERMANOVA)
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