Simplified COI barcoding of blow, flesh, and scuttle flies encountered in medicolegal investigations

Accurate insect identification is critical to the estimation of time of colonization (TOC) and post-mortem interval (PMI) in medicolegal death investigations. DNA testing is advantageous because it enables the identification of immature specimens that may not be identified based on morphology alone. We describe here a simplified DNA barcoding method for identifying relevant species that may be implemented by forensic genetics laboratories. A cytochrome oxidase (COI) fragment is analyzed after PCR amplification with a single primer set. The method is effective for many species commonly encountered in death investigations in the USA: members of blowfly genera Calliphora , Chrysomya , Cochliomyia , Lucilia , and Phormia ; members of the flesh fly genera Blaesoxipha , Oxysarcodexia , Ravinia , and Sarcophaga ; and the scuttle fly Megaselia scalaris . We tested the method on specimens with verified identifications and used it to build a collection of reference sequences from specimens collected in Harris County, Texas. We show here the correct identification of larvae, pupae, and pupal exuviae from the medicolegal casework.