Rapid approaches for accurate species identification of necrophagous insect evidence retrieved from decomposing remains is needed because of the importance of this information for the determination of postmortem interval. When the only materials available are the puparial casings from which the adult blow flies emerged, species assignment can very difficult because the casings are similar in appearance across many species. Reported here is a novel and rapid approach utilizing the soft ionization technique of field desorption-mass spectrometry (FD-MS) coupled with multivariate statistical analysis, for species identification of empty puparial cases of the 6 blow fly spp.: Calliphora latifrons, C. livida, C. vicina, Lucilia cuprina, L. sericata and Phormia regina. External validation samples were identified with 100 % accuracy. The chemical basis for the successful differentiation of species was the detection of masses associated with alkanes as large as C55H102, and sterols and esters as large as C58H118O2, many of which have yet to be reported in the literature in association with insects. Other compounds were detected that were unique to particular species, such as 3-methyltricosane (C. vicina), 11,11-dimethylhenicosane (C. latifrons), 2-methylhexacosane (C. livida) and 11-decyltetracosane (L. sericata). There were 31 m/z values which were important for discrimination that were observed by FD-MS, but which could not be detected by GC due to their nonvolatility. Observation of these higher molecular weight molecules would enable prediction models to retain higher levels of accuracy even for samples that have undergone significant weathering, because of their resistance to evaporation.
(Publisher abstract provided).
