Biology of the Membracidae of the Cayuga Lake Basin 361 



the apex itself is hollowed out anteriorly and posteriorly (Plate xxxix, 

 22, 23) — or surmounted by a heavy, punctate bar (Plate xxxix, 25). 

 The opening for the penis is almost invarial^ly on the posterior surface 

 of the apical end (Plate xxxix, 12, 20, 25, 28).- Even when the opening 

 is strictl}^ apical the oedagus is bent to turn the apex caudad so that the 

 relative position is the same (Plate xxxix, 16, 17). 



A peculiar structure is noted at the base of the oedagus in certain genera 

 of the subfamily Smiliinae (Plate xxxix, 28). This consists of a stiff, 

 toothed, internal appendage arising from the base of the curved external 

 arm and extending almost directly dorsad into the eighth segment. Its 

 function has not been determined. 



The oedagus is usually smooth and without pubescence or hairs; its 

 apex is occasionally punctured. 



These variations are believed to be entirely sufficient for taxonomic 

 use and should at least prove valuable as supplementary characters. 

 In many cases the tip of the oedagus is protruded in the mounted insect, 

 making the examination of the part possible. For this reason it is con- 

 sidered one of the most important parts of the genital apparatus from 

 the standpoint of the systematist. 



The penis is difficult to locate except in very fresh material. Since 

 its structure is a problem of internal rather than external anatomy, no 

 attempt has been made in the course of this study to work out its 

 morphology. 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 of any structure homologous to the prae- 

 penis as described by Harnisch (1915) 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 Membracidae and in 

 many forms extend far enough out of the genital chamber to make exami- 

 nation possible in the mounted specimen. Only one pair of these organs 

 is present and the relative position in the segment is comparatively uniform 

 thruout the family. Each style arises from the lateral margin of the 

 segment near its base and usually between the lateral valves and the 

 sternal plate (Plate xxxix, 14). On dissection it is seen that the base 

 extends into the abdomen and originates in the seventh segment (Plate 

 XXXIX, 5). This can be seen in a well-cleared mount of the abdomen 

 in toto. The style projects almost directly caudad and sometimes slightly 



