Some time ago in examining our species of ant lions I noticed that our two large genera, Myrmeleon and Brachynemurus, could readily be separated by the position of the origin of the radial sector; in one much nearer to the base of the wing than in the other. The characters previously used for Brachynemurns, as the forked costal veinlets, the length of the tibial spurs, etc., had not been satisfactory; and the discovery of this distinction led me to examine the other forms of the family with a view to their better classification.