Calliphora vicina (Diptera: Calliphoridae) and their ability to alter the morphology of bloodstain patterns

The behavior of blow flies (Diptera: Calliphoridae) is known to alter bloodstain patterns found at scenes of violent crime and death. However, the fundamental processes of these alterations are poorly understood. We conducted a series of experiments to investigate the feeding behavior of Calliphora vicina (Robineau-Desvoidy) and its effect on the morphology of high impact bloodstains and pools.

The experiments were conducted in microscenes (.46 m3 wooden boxes) that had two glass walls and a plexiglass ceiling made of glass to facilitate observation and photography. Multiple wall inserts were used to allow for scene changes, and the floor and wall combinations were based on materials commonly found at crime scenes. The combinations used in this study were: white linoleum floor/white painted walls, wood floor/wallpapered wall/white painted wall, and carpet/light hued paneling/white painted wall.

High impact bloodstains (stains that result from high force being applied to a blood source) were made on the walls and a blood pool was formed on the floor. The flies fed from the pool within 30 minutes of being introduced to the blood and high impact stains on the floor, walls, and ceiling. Feeding activity altered the shape of many stains while others were eliminated completely. Regurgitation and defecation resulted in the deposition of multiple new artifacts on all surfaces. Artifacts resulting from defecation were generally shaped like a tear-drop with a long tail. Regurgitated stains were generally round with little or no tail.