The purpose of this study was to evaluate the use of four fluorescent dyes (rhodamine B, uranine O, auramine O, and erythrosin B) and two nonfluorescent dyes (carmoisine and indigotine) incorporated into sugar baits as biomarkers for phlebotomine sand flies, Each dye could be detected in sand flies fed baits with dye for 24 h when examined using bright field microscopy, although there was considerable variability in the marking produced; all sand flies that had ingested rhodamine B-treated sucrose solution were marked clearly. Sand flies that had ingested sucrose solution containing rhodamine B or uranine O at concentrations as low as 10 mg/L were consistently detected under fluorescence microscopy. None of the treatments in this study reduced the longevity of sand flies. All sand flies fed sucrose solution containing rhodamine B or uranine O were marked for at least 14 d, whereas only 20% of sand flies were marked 3 d after feeding on a carmoisine-treated solution. When rhodamine B and uranine O were combined in a single sucrose solution or when the dyes were fed sequentially to sand flies, both dyes could be detected in sand flies using fluorescence microscopy. We propose that rhodamine B- or uranine O-treated sucrose baits could be used in ecological studies or to identify portions of the adult sand fly population that could be targeted with insecticide-treated sugar baits.