4 PROC. ENT. SOC. WASH., VOL. 23, NO. 1, JAN., 1921 



branous base (Ib). The appendages c are closed behind the 

 bases of the setae, which are clasped farther along by the sheath- 

 like furrow of the labrum (Lm), beyond which again they would 

 normally be held in the hollow of the labium. 



Figure 10 is a lateral view of the clypeus, labrum and hypo- 

 pharynx, showing particularly the line (MtH) of the tightly 

 closed mouth. The dorsal part of the hypopharynx (Hphy) is 

 concealed in the median depression of the epipharynx (Ephy). 

 The swelling (//) below the hypopharynx encloses the salivary 

 pump, seen in the sectional view (fig. 15, SalPmp). 



Figure 11 is the same as figure 10 but with the mouth arti- 

 ficially opened, fully exposing the hypopharynx (Hphy}. 



Figure 12 is a ventral view of figure 10. The hypopharynx 

 (Hyphy] and its wings (a, a) are seen fitting snugly against the 

 upper part of the epipharynx along the mouth line (A///z), and 

 the median part of the hypopharynx into the median depression 

 of the lower part of the epipharynx (Ephy] . The opening of the 

 mouth pore (mth) is just above the tip of the hypopharynx and 

 just within the furrow of the labrum (Lm). The setae lie length- 

 wise in this furrow, to which they converge from their bases 

 close along the sides of the hypopharynx, the inner or second 

 pair closely embracing the hypopharyngeal tip. 



Figure 13 shows the setal pouches of the left side exposed by 

 the separation of head sclerites A and B, most of which are also 

 removed. The setae appear to be produced into the head cavity 

 as apodemes for the muscles that operate them. The first seta 

 has two apodemal arms: one (JRAp) a long slender rod having 

 the retractor muscles (iRmcl) inserted upon its upper end; the 

 other (IPAp) a wide plate bent over at the top, where it is 

 loosely connected with plate A, having the protractor muscles 

 . (iPMcT) inserted upon its anterior face. The retractor muscles 

 are attached on the dorsal wall of the epicianium posterior to the 

 ocelli. The protractors go downward and forward to their 

 attachment along the front part of sclerite A and against the 

 high apodemal ridge between this sclerite and the lower part of 

 the front (Ft). The second seta (2Sef) has only one apodemal 

 arm (2Ap) which carries the insertion of the protractor muscles 

 (2PMcT) and that of one of the retractors. The other retractor 

 is inserted directly upon the base of the seta. Both bundles 

 (2RMcl) are attached to the vertex* bet ween the inner margin of 

 the compound eye and the bases of the retractors of the first 

 setae. The protractors (2PMcT) are attached to the lower part 

 of head sclerite B and to its lobe b. The apodeme of the second 

 seta and the protractor apodeme of the first are connected by a 

 thin sheet of muscle fibers indicated by the set of parallel lines 

 crossing the setal bases. The outer edge (/) of the protractor 

 apodeme of the first seta (IPAp) forms the chitinous strip in the 

 thin membranous floor of the deep groove between sclerites A 



