Initial insights into using outline-based geometric morphometrics of the larval cephaloskeleton to identify forensically important calliphorids in Thailand

Blow flies (Diptera: Calliphoridae) play an important role in forensic entomology (using insects and other arthropods to criminal investigations). An early step for this application is accurate species identification. The 2 main approaches are morphological and molecular, but each has its limitations, making it necessary to use alternative or supplementary tools. Since outline-based geometric morphometrics (GM) is widely applied with insect identification, this study examined this method for species identification of 800 third-instar larvae of 8 blow fly species Chrysomya chani Kurahashi, Chrysomya megacephala (Fabricius), Chrysomya (Ceylonomyia) nigripes Aubertin, Chrysomya pinguis (Walker), Chrysomya (Achoetandrus) rufifacies (Macquart), Hemipyrellia ligurriens (Wiedemann), Lucilia cuprina (Wiedemann), and Lucilia porphyrina (Walker). Successful classification based on the cephaloskeleton demonstrated high reclassification scores ranging from 89% to 100%. This indicates that outline-based GM of the larval cephaloskeleton contour offers a significant advantage in identifying fly specimens. It can complement traditional methods, especially when encountering certain limitations-such as incomplete or damaged larvae-and can also help lower costs associated with molecular analyses.