Species Identification of Sarcosaprophagous Flies Based on Vein Digital Image Analysis / 法医学杂志

Objective To identify species of common sarcosaprophagous flies based on digital image analysis of veins, in order to provide new idea for fast and accurate species identification of sarcosaprophagous flies in forensic entomology. Methods Random trapping of 226 male and female sarcosaprophagous flies that comprised of 7 common species, including Sarcophaga peregrina, Parasarcophaga ruficornis, Sarcophaga dux, Seniorwhitea reciproca, Bercaea cruentata, Aldrichina grahami, and Synthesiomysia nudiseta with carrion in the field was conducted. The 17 landmarks on the right wing of each fly were digitally processed and the images were analyzed. The effects of allometry were evaluated using a permutation test. Wing shape variations among 7 sarcosaprophagous fly species and female species was analyzed using canonical variate analysis （CVA）. Additionally, cross-validation test was used to evaluate the reliability of classification. Results Among 7 sarcosaprophagous fly species and female species, the effect of allometry had statistical significance （P<0.05）. The CVA results showed that among 7 sarcosaprophagous fly species and female species, differences in the wing shape were significant, and the first two canonical variates accounted for 82.9% and 84.1% of the total variation of vein shape. Vein digital image analysis can be used to separate the 7 common sarcosaprophagous flies, with an overall species identification accuracy of 81.2%-100.0%, and with a species identification accuracy of 75.0%-100.0% to distinguish the female flies of the 7 sarcosaprophagous flies species. Conclusion Vein digital image analysis is a relatively convenient and reliable method for identification of insect species, which can be used for species identification of common sarcosaprophagous flies.

Research Progress on Species Identification of Sarcosaprophagous Flies / 法医学杂志

Estimation of postmortem interval （PMI） has always been one of the difficult problems for forensic scientists. It is especially hard to estimate the PMI of highly decomposed corpses in the wild or in secluded houses with conventional methods. Therefore, application of insect evidence at the scene is usually required for estimation. Sarcosaprophagous flies of different species have totally different developmental rates. In actual cases, direct measurement of the body length of the larvae, calculation of accumulated temperature and succession stages without species identification, or calculation based on incorrect species identification would often lead to a large deviation between the calculated results and the real PMI. This mistake would also mislead the case investigation. Therefore, accurate species identification should be implemented before any PMI estimation of decomposed corpses with forensic entomological methods. This article reviews the general and ultramicroscopic species identification and molecular biological species identification methods of different stages of sarcosaprophagous flies, in order to provide new ideas and methods for related research and practice, and provide reference for the application and promotion of forensic entomology in the front line of public security.

Identification of Common Sarcosaprophagous Flies in the Yangtze River Delta by COⅠ Gene / 法医学杂志

OBJECTIVES@#To identify the common sarcosaprophagous flies in the Yangtze River Delta based on mitochondrial cytochrome c oxidase subunit Ⅰ(COⅠ) gene sequence and verify the reliability of this method.@*METHODS@#Seven common genetically stable sarcosaprophagous flies in three families and six genera were collected from large domestic pig carcasses placed in the field and cultured in the laboratory for many generations. The whole genome DNA was extracted and the COⅠ gene fragment was amplified. The forward and reverse sequencing was followed by splicing. The base composition of the amplified fragment and the rate of interspecific evolutionary divergence were analyzed by software such as Mega 7.0.26. The phylogenetic tree of COⅠ gene sequence of common necrophagous flies in the Yangtze River Delta was established by neighbor joining (NJ) method and unweighted pair-group method with arithmetic means (UPGMA) method.@*RESULTS@#The average base composition of different flies was A(30.14%), T(38.23%), C(15.98%), G(15.65%). The rate of interspecific evolutionary divergence ranged from 2.2% to 15.3%, the lowest rate was between Chrysomya megacephala and Chrysomya pinguis, the highest rate was between Muscina stabulans and Boettcherisca peregrina.@*CONCLUSIONS@#COⅠ gene can be used to identify the common necrophagous flies in the Yangtze River Delta.