The brief paper here presented is but the first of a series of studies which the writer proposes to work out concerning the ecological relations of the animal life of Johnson County. Johnson County has been chosen as the field for observations for several reasons, among which are its availability from Iowa City and the University buildings as a center, its wealth of diversified habitats, and the most excellent work already done by Professor Bohumil Shimek in the field of plant ecology, upon which all studies of animal ecology depend, as all animals ultimately depend upon plants for food