Cuticular hydrocarbon analysis for the identification, ageing and geographical variations of forensically important blowflies

Calliphoridae (blowflies) are important for forensic entomology as they are often the first group of insects to inhabit decomposing remains. To estimate the minimum post-mortem interval (PMImin), blowfly samples are collected from the crime scene and identified, and then the age needs to be determined for each species. Accurate species identification is crucial, as varied species have different life-stage timings. Previous studies on Diptera have shown the possibility of using cuticular hydrocarbon (CHC) analysis to aid species identification, ageing and ultimately calculating PMImin. However, since prior research was conducted at constant temperatures, the effect of fluctuating temperature on chemical profiles and the stability of CHCs in the field remains unclear. This thesis aims to examine the CHC profiles of Lucilia sericata and Calliphora vicina reared outdoors in the United Kingdom, Germany and Turkey in terms of species, age and inter-population differences. The first study investigates whether the stability of the CHC profiles of two colonies reared outdoors can be used to identify species-specific characteristics. The second examines the effects of fluctuating and constant temperatures on the CHC profiles of the life cycle stages and the use of their chemical profiles for age estimations. The final study aims to determine the differences in CHC profiles of the same species living in different habitats and whether they can be used to distinguish populations. The CHC profiles of the samples were extracted and analysed using Gas Chromatography-Mass Spectrometry (GC-MS). The statistical interpretation was carried out using Principal Component Analysis (PCA). The results showed that CHC profiles differed significantly between developmental stages by species, age, rearing temperature and geographical location. This study highlights that despite environmental factors affecting the stability of CHC compositions, the CHC analysis can be used as a complementary tool for identifying and ageing the species. Furthermore, the effects of ambient temperature and geographical variation on CHC profiles may be useful for determining inter-population variations.