3o HOMOPTERA 



sclerite appeais as a subtriangular piece 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; 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 shows from a caudal view 

 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. In some species the tergum is armed with teeth 

 on each side, such teeth probably functioning in the process of copulation. Occasionally the tergum 

 shows a process, or projection, on the median dorsal line, which is probably the remains of the 

 nymphal spines of that region. In many cases the sclerite is pubescent, and the hairs may be devel- 

 oped to such an extent as to overhang and hide the rectal opening. The variation in lateral length 

 may range from an almost complete arch to a very narrow strip extending hardly one-third of the 

 distance toward the pleural line. 



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, for systematic purposes, 

 the character mosteasily determined is whether they project directly caudad to continue the lateral line 

 of the abdomen, or turn inward to meet under the rectum and form a posterior wall for the body cavity 

 and an anterior wall before the oedagus. This is believed to be a constant and valuable generic charac- 

 ter. In size the valves vary from narrow triangular sclerites to broad, flat plates which occupy most 

 of the lateral surface of the segment. They are often armed with teeth, but the position of these teeth 

 is variable. 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. 



The cedagus, or penis sheath, is a heavy, paitl}- chitinized covering for the penis. It is appar- 

 ently of one piece and does not show the segments described for this organ in other orders of insects. 

 In composition it is substantial enough to withstand the boiling and clearing necessary for examination 

 underthe microscope, and usually stands out well in such mounts. The cedagus seems to arise from 

 the very base of the ninth segment, between the bases of the lateral valves and the sternal plate. Such 

 an origin would agree with that found in certain beetles, and fairly well with the same structure in other 

 orders. The function of the organ is undoubtedly protective, and it may be noted that practically no 

 olher protection is aiforded to the penis since the entire genital chamber is so openly exposed. The 

 cedagus itself is apparently of sufficient strength and rigidity to need no other protection, although in 

 most other orders it is covered by some parts of the genital chamber. In shape the oedagus is uniformly 

 curved, bending upward and forward so that its apex points toward the rectum. It varies greatly in 

 diameter in different genera and the tip is inclined to be much modified. Often the entire organ is 

 gradually acuminate and sharp at the extremity; again, the tip may be swollen and surmounted by a 

 knob-like projection. Such variations may be of taxonomic importance and should at least prove 

 valuable as supplementary characters since in many cases the tip of the oedagus is protruded in mounted 

 insects, making the examination of the part possible. 



The penis is difficult to locate except in very fresh material. On superficial examination it 

 appears to be a long, whitish filament, its length being surprising as compared with that of the 

 oedagus. No indication has been found homologous to the « praepenis » as described by Harnisch 

 (igiS) for certain Coleoptera, nor do there appear to be any important variations in the basal structure 

 of the organ. 



The styles, or forceps, are very apparent in the Membracida and in many forms extend far enough 

 out of the genital chamber to make examination possible in the mounted specimen. Only one pair of 



