SUMMARY.1An area was chosen which was as typical as possible of the permanent pasture fields of the district, and in which invasion by insects not belonging to the area would be reduced to a minimum.2In order to define the characters of the area under consideration as clearly as possible, chemical, mechanical and botanical analyses were carried out.3Insects, largely in immature forms, were obtained by examining samples of soil from various parts of the area, and in addition many adults were obtained by sweeping the herbage with a net. The latter method produced also some invading forms which did not belong to the area.4The factors influencing the distribution by depth of the insects in the soil were in this case chiefly occurrence of food, aëration, and moisture, and the result of these influences was that the insects seldom penetrated even as deep as six inches, the vast majority of specimens being found at a depth not greater than two inches.5The census of insects actually found in the samples of soil gave an insect population of 3,586,088 per acre. The family best represented in number of individuals was the Bibionidae, species of which made up 32–4 per cent, of the total number of soil insects. The next in number were the Mycetophilidae 16–7 per cent., and the Staphylinidae 12–2 per cent. With regard to number of species occurring in the soil, the Coleoptera, with 29 species, was the best represented