Evaluation of species, biological sex, and post-collection sample handling effects on the volatile odor profile of immature blow flies

In medicolegal death investigations, forensic entomology plays a role in determining the time interval in which saprophagous insects have colonized the body. When larvae are present, this is commonly accomplished by hot-water killing the larvae, measuring length, and comparing length measurements to known growth curves for the same species reared in the same ambient temperature as those from the carrion. Currently, no separation exists between males and females for blow fly growth curves which may cause a decrease in precision of this postmortem interval. Methods for identifying sex and species that may aid in creating these sex-separated growth curves are time consuming and sample destructive. Chemical volatile analysis is growing within the literature as a potentially quick, non-invasive method for species identification and larval aging of entomological samples as well as a tool for identifying stages of decomposition within carrion. Utilizing solid phase microextraction with gas chromatography mass spectrometry as a method of chemical volatile analysis for blow fly larvae and eggs, this study evaluates the feasibility and impact on odor profiles obtained from a single Cochliomyia macellaria larva. Additionally, the utility of VOCs as a non-destructive method to identify larval sex and species was also investigated. This study found that odor profiles can be obtained from single larval samples and that there is a potential 6-fold decrease in volatile abundance from live to boiled samples. An overall 96% success rate was achieved for identifying biological sex through molecular methods; however, no odor profile differences between males and females in this study were observed. Finally, this study was also able to obtain odor profiles of small egg clutches for Co. macellaria and Phormia regina; however, these odor profiles were unable to be differentiated at a trace level.