The writer has been working on the food plants of the leaf-hoppers for many years and has found in the main the different species of the genus Platymetopius, as commonly recognized, are very closely confined to a single species of plant or to a closely related group. Before it was possible to prepare a list of the food plants in the group it was found necessary to describe a number of new species of which food plant and life history information was available. In working out the relationship of these species, two startling discoveries were made.