A study was undertaken at the Hawaiian Fruit Flies Laboratory in Honolulu, Hawaii, to find a possible internal marker for the adult melon fly,Dacus cucurbitaeCoquillett, that would be detectable in release-capture studies. The marker of choice would be a dye that could be fed in the larval diet. We found that the fly was colored black when Sudan® Deep Black BB was fed in this way. We therefore investigated the marking, the most promising dose, and the effect of the dye on the mating and flight behavior, and longevity of dyed and undyed flies.