BRANCH: BIOLOGY OF KANSAS MEMBRACID^. 93 



An endeavor has been made to locate the nerves governing 

 *^^he mouth parts, but as yet without success. 



Clypeus. In sections shown at figure 47, plate XIII, and 

 figure 48, plate XIV, the heavy muscular tissues on the interior 

 of the clypeus are seen. They are transverse and longitudinal 

 muscles, which presumably regulate the muscular contraction 

 and retraction of the upper part of the pharynx, and for this 

 reason are called the pharangeal muscles. 



Summary. 

 In a median lateral longitudinal section of the entire head 

 and beak, a final and more comprehensive conception of the 

 entire structure is presented. A careful study of this section, 

 combined with the others just referred to, give the following 

 results (fig. 50, pi. XV) : 



The Pharynx enters the head in a plane at an angle of 

 about 60 degrees with the vertical or cephalic face of the head. 

 It passes over the suboesophagal ganglion, and, turning sud- 

 denly downward, passes under the superoesophagal ganglion 

 (see b) . The pharynx proceeds toward the ventral face of the 

 head until near the base of the distal end of the clypeus (z) , 

 when it turns sharply downward in a line parallel to the ven- 

 tral face of the clypeus. At this turn the upper wall of the 

 pharynx is formed by the hypopharynx (h) , which joins itself 

 to the epipharynx ig), lying beneath the labrum (l). The 

 upper wall of the pharynx is expanded and compressed by the 

 heavy muscles in the clypeus and labrum (t, u, n). The max- 

 illary setfe (;r) lie either side of the pharynx, gradually ap- 

 proaching each other until they meet, one lying over the other, 

 forming a complete tube to continue the alimentary canal to 

 the end of the maxillary setae. 



Pump. (Fig. 50, p, pi. XV.) Situated below the pharynx is 

 a fleshy bundle of muscles with an opening into a short duct, 

 wihch appears closed at the forward end. From this duct are 

 two smaller ducts (k and o, fig. 50), one leading into the 

 pharynx, and the other presumably leading from the salivary 

 glands. 



Beak or Labium. The floor of the mouth is formed by the 

 extension of the first segment of the beak (/, fig. 50, pi. XV), 

 and is supplied with muscles near the curve of the first seg- 

 ment. These muscles are presumably used in lowering and 

 raising the beak. Each segment has three pairs of lateral 



