The pupal parasitoids of summer and winter pupae of the fall webworm, Hyphantria cunea, were investigated from March 1978 to August 1982. Pupae and parasitoid emergence from band traps set on road side trees was studied to determine ways to insure the effectiveness of parasitoids as natural enemies of fall weborm larvae, thus minimizing the necessity of using insecticides, potentially harmful to parasitoids and to man, to control the fall webworm. In this study 24,180(68%) adult fall webworms emerged from 35,538 collected pupae. The pupae collected from groups of Platanus trees(tree diameter at breast height 60cm.) were the largest in site. Platanus trees proved to be supplying more pupating sites than other trees, probably because large pieces of the bark peel off providing many protected spaces beneath which the final instar larvae can pupate. A total of 2,776(7.5%) of the pupae had parasitoids. More parasitoids emerged from pupae collected from areas where insecticides were not sprayed than from those where they were used. The highest rate of parasitism at a single locality was 25.8%. Fourteen species of hymenopterous and two species of dipterous parasitoids were collected. In addition, fourteen species of predators were observed during this survey. Thirty nine species of spiders(belonging to ten families and 26 genera) were collected from winter band traps. Eight of these species prey on larvae of H, cunea in summer was proved. Generally, pupating begins as early as June 26th for larvae from overwintering pupae(first generation) and around August 26th for new larvae(second generation). The setting of band traps should be finished before these dates. Thus setting band traps twice a year is more effective than a single setting. Generally, the parasitoids in overwintering pupae emerged in April but the fall webworm adults emerged in May. This suggests that band traps should be burned around the last of April, about ten days before emergence of the fall webworms. Parasitoids and fall webworm adults emerged from diapausing pupae at the same time in July. Keeping the removed straw mats in a warehouse with netted windows(mesh size 3.0mm$ imes$3.5mm) allows only parasites to escape. In this way straw mats mar be used more than once and additional parasite preservation is insured.