This paper deals with the life history of Rhagoletis pomonella Walsh in Maine. It presents data which indicate that time of fly emergence is governed by a number of factors. Some of these factors are: variety of fruit in which the larva develops; nature of the soil (light or heavy); location; and amount of rainfall during the emergence period. In order to obtain large quantities of the larvae for various purposes a special trap was developed. A small fall or second brood of flies has been produced in our cages each year in one section of the State but not in others where the soil is heavier. Only larvae which develop in early or summer varieties transform to flies the same season. Practically all the second generation flies appear during the first two weeks in October-hence they are not of economic importance. Two-year cycle flies are likewise recorded. Counts covering the daily sex records of nearly 23,000 flies in 1932, indicate that the period during which the males and females emerge in nearly equal numbers coincides with the peak of emergence.