This publication is a companion volume to Miscellaneous Publication 273, Insect Enemies of Western Forests, but Keen. Its purpose is to treat in a practical manner the more important forest insects in that part of the United States lying east of the Great Plains or treeless areas, roughly the 100th meridian. There is necessarily some overlapping of the eastern and western regions, particularly in the more arid parts of Texas and the Southwest and along the watercourses traversing the Great Plains where the eastern hardwoods extend westward.