Like all Diptera with sponging mouthparts, M. domestica adults liquefy solid food externally by regurgitating oral secretions onto the substrate prior to imbibing the dissolved food (Stoffolano, 1995). House fly oral secretions are a composite of salivary gland secretions and contents of the crop, a diverticulation of the foregut that plays an important role in the regulation of feeding and the utilization of ingested food (Haselton et al., 2006).