Wing morphometrics for the identification of Nearctic and Palaearctic Piophilidae (Diptera) of forensic relevance.

The Piophilidae (Diptera) are a family comprising about 80 species, several of them of high economic and forensic relevance. An unequivocal species identification is crucial for designing effective control measures or to provide reliable estimations of the minimum post mortem interval. However, the identification may sometimes not be possible, either because the diagnostic morphological characters are not easily observable or very fragile, or because of a poor DNA quality and/or unavailability of reference molecular signatures. In the recent years, the use of wing morphometric techniques has emerged as a powerful tool for the identification of different families of forensically important Diptera. The present study applies, for the first time, this technique to the identification of 11 Piophilidae species of forensic relevance in the Nearctic and Palaearctic regions, as well as to the discrimination of sexes, distinct geographical populations and, in the case of the dimorphic species Prochyliza nigrimana (Meigen), seasonal morphs. Wing shape variation was analysed using 14 landmarks located at wing vein junctions and a cross-variation analysis was used to test the reliability of identifications. The present results demonstrate that wing shape can be used to identify most species with relatively high success, whereas cross-validation analyses indicated that discrimination between sexes, populations or morphs was less effective, even if significant differences were observed in every comparison. We conclude that wing morphometrics can be a powerful identification tool that might be used in combination with other methods in order to achieve accurate and reliable species identifications-independently of the sex, geographic origin or colour variation of the samples-even with those piophilid species that have been object of frequent misidentifications.