Little is known about the main predators of emerging pests in Bt cotton. To fill this gap a marking technique using ELISA (enzyme-linked immunosorbent assay), was adapted to assess predation on mirids, Helicoverpa eggs, and cotton aphids. The technique involves marking target pests with rabbit IgG protein and then using ELISA to detect the presence of the protein in predators who may have consumed the pest. The technique was first tested under laboratory conditions, and then applied under field conditions.