34 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 



anterior part of the thorax this diaphragm is merely a very delicate 

 membrane attached laterally on the salivary glands and on masses of 

 fat tissue. Between the w^idely spreading bases of the metasternal 

 apophyses, however, there begins in the membrane a series of trans- 

 verse muscle fibers, which continues to the posterior end as the prin- 

 cipal tissue of the diaphragm. The fibers are attached in the meta- 

 thorax to the metasternal apophyses, and in the abdomen on the lateral 

 parts of the sternal plates (fig. 15 C). Most of the fibers go continu- 

 ously across from one side to the other, but in each segment the 

 anterior and posterior fibers spread somewhat forward and backward 

 to bridge the spaces between the consecutive sternal plates. Posteriorly 

 the ventral diaphragm ends al:)ruptly in a free transverse margin, which 

 in the female crosses the anterior part of the seventh abdominal seg- 

 ment, but in the male is in the anterior part of the eighth segment. In 

 the female the last two ganglia of the ventral nerve cord lie beyond 

 the diaphragm and are dorsal to the spermatheca, the anterior end of 

 which may extend into the ventral sinus. In the male only the last 

 ganglion is not covered by the diaphragm. 



IV. THE PROCTODAEUM 



The proctodaeum of the grasshopper is a tube of fairly uniform 

 diameter composed of anterior and posterior sections separated by a 

 narrower and usually bent middle section (fig. 16 A), but the relative 

 size of the parts varies much in different specimens according to the 

 distension, or according to the state of contraction of the muscles. 

 The anterior end of the proctodaeum is marked externally by the 

 origins of the Malpighian tubules (Mai), which are disposed in 12 

 groups of about 10 tubules each, arranged in a circle immediately be- 

 hind the ventriculus (Vent). There is no clear anatomical division of 

 the proctodaeum into an anterior intestine and posterior intestine, 

 and there are no specifically developed internal valves, but four fairly 

 well-marked proctodaeal regions may be distinguished by external and 

 internal characters. The first is a short pylorus (Py) into which the 

 Malpighian tubules open, the second is a long saclike ileum (//), the 

 third a narrower and usually bent colon (Cln), and the fourth is the 

 large rectum (Red) comprising a wide anterior rectal sac and a 

 narrow terminal part extending to the anus. 



The muscularis of the proctodaeum consists of external longitudinal 

 fibers and internal circular fibers, the relation of the two sets of 

 muscles on the proctodaeum being thus the same as that of the ven- 

 tricular muscles (fig. 16 A), though the muscle fibers of these two 

 parts of the alimentary canal are not continuous with each other. 



