iophagiis, Bnicsia and in the species examined of a genus allied 

 to Xenos, in fact in all the male Stylopids considered in this 

 paper, and as it furnishes an easy means of identifying- homo- 

 logous parts of the face, it is of great importance. 



If we now consider the parts of the face in Elcnchus as com- 

 I)ared with Bnicsia the most striking difference noticed at once 

 is the fact that the part immediately above the foramen (which 

 corresponds to b in the diagrammatic figure) appears to end 

 above in a free edge and not to be sutured to the frontal process. 

 It is this edge that Eaton considers the apex of the Ugnla, and 

 the cavity between it and the frontal process as the oral open- 

 ing. I believe however that this edge is not the real extremity 

 of this plate but is due only to a sharp bend therein. We arc 

 therefore left with two alternatives: if we consider with Eaton 

 that there is a great ligitla, then in Bruesia and Halictophagus 

 schivarsii the apex of the ligula is not free, but continuous with 

 the frontal process, and not even divided therefrom by a dis- 

 tinct suture; or if we adopt the interpretation that I favor, we 

 shall consider the same part as epistome, or epistome and lab- 

 rum, though in some genera its basal (upper) margin is deeply 

 imbedded in the excavated front of the head. A strong immer- 

 sion of the clypeus beneath the level of the front, or of labrum 

 beneath the clypeus, is by no means unfamiliar in other orders 

 of mandibulate insects. In a species of a genus allied to Xcnos, 

 the head of which is figured on Plate I, fig. 4, it will be seen 

 that the epistomal portion lies entirelv immersed beneath the 

 prominent edges of the sides of the face. As to the division of 

 the lower part of the face into epistome and labrum, both in a 

 dry specimen of Bruesia and in one mounted in balsam, I think 

 1 can detect faint sutures, marking off a labrum from the epis- 

 tome, and I suspect that the foramen always marks the division 

 between these. 



THE THORACIC SEGMENTS. 



The pro- and meso-thorax appear to be always small and ring- 

 like, and one or both of these are immersed in the posterior con- 

 cavity of the head (PI. I, fig. 3), and on superficial examination 

 may even appear to be part of this. 



In some figures of Stylopidae the top of the head is repre- 

 sented as much more solid than it reallv is, the pronotum prob- 

 ably having been considered as part of the vertex. The meta- 

 thorax differs greatly in the arrangements of its parts in differ- 

 ent genera. In Elenchus (PI. II, fig. 11) the posterior of the four 



