Characterization of Insect Stains Deposited by Calliphora vicina (Diptera: Calliphoridae) on Shirt Fabrics

Abstract

Despite the fact that necrophagous flies are known to alter bloodstains and create unique artifacts, no research has occurred to date that has examined the characteristics of insect stains on textiles or fabrics. This study represents the first effort to characterize artifacts produced by adult Calliphora vicina Robineau-Desvoidy deposited on a range of shirt fabrics that varied in type, color, orientation, and yarn tension. In general, artifact morphology on any type of fabric was distorted in comparison to those observed on smooth and/or nonporous surfaces in previous studies. Consequently, distinction of artifact type could only be made broadly as digestive artifacts and transfer patterns, in which the latter was predominantly detected as tarsal tracks. None of the artifacts displayed satellite stains typical of human bloodstains found on textiles. Wicking was evident on all fabrics but was most pronounced with dri wick and jersey knit polyester in comparison to cotton knit. Digestive artifacts on any colored fabric, but especially with green and yellow shirt samples, resembled the reported color, size, and morphology of bloodstains generated in laboratory studies on a range of fabrics. Unique digestive artifacts were also detected as small, black, and nearly spherical. These defecatory stains did not appear to wet or wick into any of the fabrics. Digestive artifacts and tarsal tracks differentially interacted with front face stitch loops of clothing fabrics to yield distinct stain patterns. The implications of these observations in reference to bloodstain pattern analysis at crime scenes are discussed.

Keywords: artifact morphology; bloodstain; blow fly; fly artifact; forensic entomology.