Retention of Human Body Fluids in Adults of Calliphora vicina (Diptera: Calliphoridae)

Foraging by Calliphora vicina Robineau-Desvoidy often leads to a period of bubbling behavior, followed by either deposition of the regurgitate onto surfaces or reuptake of the bubble. Eventually, the partially or undigested food is passed in the excreta forming fecal or defecatory stains on surfaces in which deposition occurs. This study examined the digestive artifacts (i.e., regurgitate and defecatory stains) formed following consumption of human blood and semen by adult flies in an attempt to determine the length of time the meal was retained in the crop. The morphological appearance of either type of stain appeared consistent with the color of blood or semen for 10-20 d after feeding. When tested with ABA Hematrace immunochromatographic strip assays, blood was detectable in at least 33% of fly artifacts 25 d after the initial consumption of blood. Similarly, semen was detected in nearly 34% of digestive artifacts 30 d after feeding on human semen when using ABA p30 cards. Human body fluids were also detected in fly artifacts when using RSID lateral flow assays, but a much lower percentage of artifacts tested positive for blood (4.9%) and semen (4.6%) 25-d postfeeding in comparison to ABA strip assays. The difference between the types of lateral flow assays appeared to be due to extraction efficiencies of the buffers used for isolation of blood or semen from the fly artifacts. The implications of these observations in reference to seasonal adaptations and to bloodstain pattern analysis at crime scenes are discussed.