branch: biology of KANSAS MEMBRACID^. 89 



Muir and Kershaw easily opened and the two sclerites sepa- 

 rated. In figure 42, pi. XII, can be seen this sclerite with 

 the labriim remoA'ed. It has a delicate di.stal process, which is 

 covered and protected by the labriim. The cross on figure 42 

 shows where the seta is joined to the sclerite on its inner sur- 

 face. This sclerite is also sparsely covered with hairs. It can 

 not be seen in caudal aspect until the maxillary sclerite has 

 been removed. (Fig. 41, pi. XII.) 



Maxillary Sclerites. (Fig. 37a at n, pi. XI.) Situated 

 laterad and below the mandibular sclerites are the maxillary 

 sclerites. They too are curved, but on the front face are much 

 narrower than mandibular sclerites. They form the lateral 

 surface of the plane, however, and in caudal aspect are wide. 

 (Fig. 40 at X, pi. XII.) Each sclerite bears two processes, 

 one above the other, and both grooved on their outer edges to 

 assist the set£e better on their way into the head. The proc- 

 esses are also concealed under the labrum. Figure 39, plate 

 XII, shows the inner surface of the clypeus, mandibular 

 sclerites, labrum, and epipharynx. Situated on the distal edge 

 of the clypeus and at the base of the epipharynx is the heart- 

 shaped hypopharynx. Its function seems to be to cover the 

 setse as they merge together and continue the tubular structure 

 of the pharynx and enter the grooved trough of the epi- 

 phamyx. 



Labium. (Fig. 37a, pi. XI; fig. 38b, pi. XII.) This is the 

 beak in which lie the setse. It is composed of three segments, 

 the second of which in cephalic view appears longest, but in 

 lateral aspect seems to be joined to the distal segment by a 

 sort of socket joint, the dorsal edges of which are formed by 

 this second segment and the distal segment set into this socket 

 thus formed. (Fig. 38a, pi. XII.) The first segment of the 

 beak, as it passes under the labrum, clypeus and maxillary 

 sclerites, broadens until it seems to form the base of the caudal 

 cavity of the head. This segment forms the floor of the mouth, 

 and, although chitinized, it is flexible. It is "supported down 

 the middle by a chitinized rod (fig. 40 at r, pi. XII) coming 

 from the bar and joining the tentorial sclerites. This rod ex- 

 tends the entire length of the beak, ending in the third seg- 

 ment. On dorsal side the labium is closed and flat, but on the 

 ventral side its edges curve inward to form a groove or trough 

 for the setae. The first two segments of the beak are slightly 



2-Umv.Sci. Bull.. Vol. VUI. No. 3. 



