present in the hemolymph of replete females only at 10-8 M. Thus, hemolymph components at this concentration or below may be affected by specific antibodies directed against them. The main advantage of using ELISA for detection of host antibodies in the hemolymph of ticks was the small volume of hemolymph required (about 0.2 Al/tick). Thus, all adult ticks and most nymphs can be tested individually with this assay. This assay may be used to evaluate the potential for controlling other hematophagous arthropods with IgG against their hemolymph components.