In observations on the root maggots of garden crops in Canada made by A.R. Brooks in 1947 and later mimeographed (1) for officers of the Division of Entomology, Mr. Brooks indicated that there is frequently a complex of species in a field sample of larval Diptera; that the species and their numerical proportions are likely to vary both seasonally and geographically; and that not just one but 15 species of Diptera have been found in the roots of cabbage and as many as 14 in onions. He observed further that certain species of maggots appear directly responsible for the plant injury; others play a secondary role so that there is sometimes an involved ecological succession of species.