Appreciable losses are annually sustained by Utah alfalfa-seed growers due to shriveled seed. To ascertain possible relationships of the bugs (L. hesperus and L. elisus), heavy infestations of which occur in alfalfa seed fields, field expts. were performed during 1932, 1933, and 1934 in which these insects were caged on seed-producing alfalfa. Results indicate that Lygus bugs increased the number of shriveled seeds in direct proportion to the intensity of infestation and that they were not the exclusive cause of shriveled seed.