Traps have been found useful in monitoring and reducing populations ofSapyga pumilaCresson an important parasite of the alfalfa leafcutting bee,Megachile rotundataFabricius. Traps painted white, light blue or green were more effective than brown or red. Traps painted white, shades of light blue or coated with transparent plastic were equal in trapping efficiency to the natural unpainted traps.S. pumilawas more responsive to the contrast between hole in the trap than to trap color. Largest numbers ofS. pumilawere caught in traps placed on the front of leafcutting bee domiciles.