This is a reprint of the second (1967) edition, with the addition of several references, and notes on the present status of Chloroperla and recent findings on the nymphs of Isoperla. The distribution maps of the second edition are reproduced unchanged. It has not been found possible to update them or re-plot them on the 10 km grid, but it was felt that a number of interesting points regarding distribution would be lost if they were omitted.