PROC. ENT. SOC. WASH., VOL. 23, NO. ], JAN., 1921 



Figure 7 is a ventral view of the adult head. The mouth 

 (Mth) is forcibly opened by prying the clypeus forward with 

 the dissecting needle; and the base of the labium (Lb) is 

 turned back, thereby pulling the setae away from the hypo- 

 pharynx. The lateral head sclerites (A>A} are seen to be 

 directly continuous with the wings (a,a) of the median hypo- 

 pharynx (Hphy}. Behind the latter are the two deep pouches 

 from which issue the setae (ISet and 2 Set). The lobes (fig. 6, ti) 

 of the plates B,B are cut off near their bases (b) for the sake of 

 clearness. This view of the head tells its own story and little 

 more need be added by way of description. 



The mouth is deceptive in the natural condition. So closely 

 is the hypopharynx applied to the epipharynx in a mature 

 specimen that it is difficult to see that the insect has any mouth 

 at all. Yet it is really a wide slit reaching from one upper angle 

 of the clypeus to the other. When closed, the upper part of the 

 hypopharynx fits snugly into a median depression of the epi- 

 pharynx; then the narrow median channel along the ridge of the 

 hypopharynx is converted into a tube which remains as the 

 functional mouth, opening above into the pharynx and below 

 just above the tip of the hypopharynx. This condition can be 

 mentally pictured from figure 7 if it be imagined that the 

 clypeus is allowed to drop down again against the hypopharyn- 

 geal wings (a, a). The median part of the hypopharynx would 

 then be received into the epipharyngeal cavity above it, and its 

 channel, now transformed into a tube, would open into the base 

 of the furrow in the labrum (Lm). Thus the wide Orthopteran 

 mouth is narrowed down to a tiny median pore to serve the needs 

 of the sucking Hemipteron. 



Figure 8, showing a front view of an emerging cicada's head, 

 from which the clypeus and labrum have been removed, gives 

 the same parts from a different angle. The labium is not shown, 

 in order to give a clearer view of the bases of the setae. Where 

 the clypeus is detached the bases of the dilator muscles of the 

 pharynx (PhyMcl) are seen, and below them the invaginated 

 roof (e) of the pharynx (seen also at e on figure 6). The second 

 setae (2 Set) are normally united along their inner faces by inter- 

 locking grooves and ridges to form a conducting tube for the 

 liquid food; but in the drawing they are separated for clearness, 

 though it is indicated how their bases embrace the tip of the 

 hypopharynx as they flare apart to enter the pouches behind the 

 hypopharyngeal wings (a,a). The liquid arising between them 

 is thus delivered immediately to the mouth pore above the tip 

 of the hypopharynx. The appendages c and c are separated, 

 but it can be seen how they would come together behind the 

 bases of the setae in the normal condition. 



Figure 9 gives a rear view, on a mature specimen, of the parts 

 referred to in figure 8. The labium is removed from its mem- 



