Morphological Features of Regurgitate and Defecatory Stains Deposited by Five Species of Necrophagous Flies are Influenced by Adult Diets and Body Size.

The morphological characteristics of artifacts from five species of necrophagous flies were examined following feeding on several types of diets. Four types of insect stains were produced by each species: regurgitate, defecatory, translocation, and tarsal tracks. Regurgitate was the most frequent type deposited (70.9 ± 2.4%), followed by defecatory (19.8 ± 4.0%), tarsal tracks (8.6 ± 1.2%), and translocation (0.7 ± 0.1%). Artifact shapes, sizes, and color were highly variable and species and diet specific. Calliphora vicina and Sarcophaga bullata consistently deposited the largest artifacts after feeding, whereas Chrysomya rufifacies and Ch. megacephala produced more tarsal tracks than the other species examined. Artifacts with tails were infrequently observed (4.1 ± 0.6% of all stains) but occurred as either defecatory or regurgitate stains. The widely variable morphologies of all types of fly artifacts underscores the view that insect stains cannot be distinguished from human bloodstains based on morphology alone.