Flies that have any direct effect on Man are only a small proportion of the eighty to one hundred thousand species which constitute the Order Diptera. "To discuss adequately a group so rich and varied it is necessary to particularize, mentioning the names of species, genera, families or larger groups," writes Professor Oldroyd. Yet, he has tried to present more of a picture of flies in evolution than a discussion of classification and arrangement. Part One is a general description of flies and their life histories: eggs, larvae, pupae, and adult flies. Part Two surveys the flies in sixteen...