meek: mouth-parts of the hemiptkra. 267 



protractor muscle (fig. 5, mdp) extends from the cephalic face 

 of the mandible to the maxillarj' sclerite (fig. 5, mds) . It is a 

 single muscle, but well developed. A quadrangular sclerite 

 (fig. 5, co) serves to connect the mandible with the head wall. 

 The joints are simple hinges, and the point of attachment is 

 the dorsal end of the mandibular sclerite. 



Figure 6 shows the enlarged tips of the stylets. The mandibles 

 are serrated on the outer edges, but the maxillae are smooth and 

 sword-like. While in position the tips of the maxillae are straight, 

 but when free from the enclosing mandibles they assume a slightly 

 recurved position. 



The relation of the stylets to each other and the surrounding 

 parts can best be studied by means of cross-sections. Figure 8 

 is such a section through the third labial segment. The stylets 

 are all crescent-shaped, and through the central portion pass 

 lumina (fig. 8,1) , which are somewhat larger in the mandibles 

 than in the maxillae. The concavity of the mandibles is so great 

 that they are almost able to enclose the small inner setae. Al- 

 though the maxillae are side by side as they leave the head, by 

 the time the third labial segment is reached, one is directly 

 above the other. The inner surface of the upper maxilla is 

 twice grooved. The three projections thus produced are mor- 

 tised into the lower maxilla. This dovetailing is nicely done, 

 and accounts for the difficulty in separating the two smaller 

 setae. It will be noticed that this device makes two tight tubes, 

 one somewhat larger than the other. Around both sets of sty- 

 lets is folded the strongly chitinized labium with its upper edges 

 very closely appressed. 



Passing from the third labial segment toward the head, there 

 is little change in arrangement or structure until the first seg- 

 ment is reached. At this point the stylets enter the enclosing 

 epipharynx (fig. 9). To this organ they are rather securely 

 fastened by a grooved contrivance. A well-defined groove passes 

 down each side of the upper part of the epipharynx and into 

 these fit projections from the closely lying mandibles ( fig. 9, mg) . 

 The maxillae are not shown in the figure, but it can be readily 

 seen how they are held between the concave mandibles. The 

 epipharynx is itself in turn similarly attached to the labial 

 wall (fig. 9, Ig). This arrangement of interlocked parts ex- 

 plains why the organs at this point are separated with so much 



