Biology of the Membracidae of the Cayuga Lake Basin 359 



extending almost to the pleural line. This tergum may project almost 

 directly caudad so that the rectum is located very near the dorsal margin 

 of the segment and very little of the tergum is visible from a caudal view 

 (Plate XXXIX, 18); or it may extend well ventrad so that the rectum 

 appears nearly in the center of the segment and a large part of the tergum 

 appears from a caudal view (Plate xxxix, 4) as a broad sloping roof. 

 In some cases the entire ninth segment is so small in diameter that from 

 a caudal view the eighth segment is visible around it (Plate xxxix, 15). 

 In some species the tergum is armed with teeth on each side 

 (Plate xxxix, 14), such teeth probably functioning in the process of 

 copulation. In a very few forms, particularly in the subfamily Mem- 

 bracinae, the tergum shows signs of median subdivision (Plate xxxix, 10), 

 but this is shown only after boiling in potash. Occasionally the tergum 

 shows a process, or projection, on the median dorsal line (Plate xxxix, 

 10, 13), which is probably the remains of the njnnphal spines of that 

 segment. In many cases the sclerite is pubescent (Plate xxxix, 15), 

 and the hairs may be developed to such an extent as to overhang and 

 hide the rectal opening. The variation in lateral length may range 

 from an almost complete arch (Plate xxxix, 15) to a very narrow strip 

 extending hardly one-third of the distance toward the pleural line 

 (Plate xxxix, 21). 



The lateral valves are always present and are of considerable importance. 

 From their position they would appear to be modifications of the pleura 

 of the ninth segment, but, as has been suggested, this may be an incorrect 

 interpretation. For systematic purposes the character most easily 

 determined is whether they project directly caudad (Plate xxxix, 24) to 

 continue the lateral line of the abdomen, or turn inward to meet under the 

 rectum (Plate xxxix, 1) and form a posterior wall for the body cavity 

 and an anterior wall before the oedagus. This is believed to be a con- 

 stant and valuable generic character. In size the valves vary from 

 narrow, triangular sclerites (Plate xxxix, 15) to broad, flat plates 

 (Plate XXXIX, 20) which occupy most of the lateral surface of the seg- 

 ment. They are often armed with teeth (Plate xxxix, 5, 8), but the 

 position of these teeth is variable as shown in the figures. Like the 

 terga, these sclerites are often pubescent. In general the lateral valves 

 seem to have little protective function, since the oedagus is well caudad, 

 and they are probably used as copulatory organs of attachment. Whether 



