Abstract
During studies of the parasite complex of the spruce budworm in the Lake Nipigon region of northern Ontario from 1946 to 1950, data were obtained on certain host-parasite relationships. The data were derived from two sources: the rearing each year of periodic collections of spruce budworms, and the dissection of budworm larvae and pupae that were collected and preserved at 2-day intervals during June of 1948 and 1949. The particular features investigated were: the sex ratio of parasites and its possible relation to the sex of the host; and the effect of parasitism on the apparent sex, rate of development, and size of the host.