The rates of parasitism of 1, 5, 10, and 50 mated pairs of the parasite,Voria ruralis(Fallen), on a known age and density of larvae of the cabbage looper,Trichoplusia ni(Hübner), in field cages were 8.9, 42.5, 62.2, and 85.1%, respectively. However, the percentages of parasitism per female at these respective densities were 8.9, 8.5, 6.2, and 1.7. Thus, an increased rate of superparasitism occurred when the density was higher than 10 females/cage.