The following four species are very closely allied and in the adults possess no very definite characters for specific distinction, even the male genitalia failing in this respect. This leads me to believe that we are dealing with a group the individuals of which have split away either from each other or from a parent form at a comparatively recent date and that even now fresh species may be in the act of formation. The nymphs offer much better specific characters and, once recognized, are not readily confused; long series of bred material may result in the discovery of good adult characters but for the present I am basing my conception of the different species largely on nymphal distinctions.