552 The University Science Bulletin. 



the metathorax. 



Tlie connection of the metathorax to the mesothorax has already 

 been noted. It is weakly joined to the abdomen, not only because 

 it is connected to the abdomen by a membrane, but also because 

 the first segment of the latter is partly membranous itself. It is 

 similar to the mesothorax in general make-up, especially in the 

 number of sclerites. 



The nohmi (pi. LVII, fig. 91, as in the mesothorax, is composed 

 of four sclerites — the prescutum, scutum, scutellmn, and post- 

 scutellum. The prescutum is peculiar in that it is entirely internal, 

 extending directly into the body cavity and lying at right angles 

 to the scutum. It is a very large, bilobed sclerite, heavily chitinized, 

 and is used for attachment of large bundles of muscles. 



The scutum is the large, heavily chitinized sclerite found on the 

 dorsal surface of this segment. It is rectangular in shape and its 

 width is one and one-half times its length. Along its median line 

 is a heavy, black line which is the external indication of an infolding 

 of chitin, which also serves for muscle attachment. 



The scutellum of the metathorax is much reduced, consisting of 

 a small, median portion, which is produced laterad into a narrow 

 band. The latter is directly connected with the anal margin of the 

 wing. 



The postsciitcllum is a flat chitinous sclerite, which is extremely 

 narrow mesad. but which expands laterad into two tapering side 

 processes. The cephalic margin of the postscutellum is attached 

 to the anterior margin of the scutellum, which is the suture sep- 

 arating the scutum from the scutellum. The diagonal, lateral angle 

 of the postscutellum is directly attached to the margin of the 

 cpimeron and no postalare is present, as in the Cicada. 



The pleuron (pi. LVII, fig. 8) is very well developed, being by 

 far the largest part of the metathorax. It not only occupies all the 

 pleural regions, but extends into the dorsal and ventral regions and 

 forms a major part of the metathorax. 



A distinct pleural suture extends the entire length of the pleuron. 



The episternuin is an undivided sclerite, although on its caudal 

 end is the beginning of a suture which runs parallel to the pleural 

 suture. The episternum is the largest of the pleural sclerites, 

 occupying the ventral half of the pleuron, the lateral third of the 

 venter, and the laterocephalic angle of the dorsum, where it curves 

 around the wing process. 



