The Neodiprion sawfly studied in this investigation is an undetermined species which attacks sugar pine, Pinus lambertiana Dougl., in California. The conditions of the infested area were particularly suitable for an investigation of some of the basic factors affecting distribution of cocoons on the ground. The efforts of previous workers (Prebble, 1943; Ives and Turnock, 1959) were complicated by dense stand conditions and deep, variable pound cover. The sawfly discussed here was found in considerable numbers on an isolated, young sugar pine at Grass Valley, California. The tree was 19 feet high, 16 vears old, with s diameter of 5.5 inches. The infestation was presumed to be recent as no effect on diameter growth was found, even though the tree possessed only the current year's foliage. The ground cover was extremely sparse and the soil was a compacted, sandy-clay, typical of many foothill areas in California.