40 The University Science Bulletin. 



often be prolonged into a distinct cephalic process. This ventral arm 

 varies greatly in different genera and species, but, as far as our 

 observations go, is always constant in shape within the species. It 

 usually extends more or less dorso-caudad, though sometimes its 

 apex is bent distinctly dorsad and may even extend dorso-cephalad. 

 The course of the penis through this arm is usually easy to trace in 

 caustic potash specimens. 



In the genera Ceresa and Stictocephala the functional orifice is 

 usually along the ventral side of this arm and at quite a distance 

 from the apex. This opening in these genera is usually quite long 

 and is guarded by a distinct membranous external sheath. In S: 

 jestina, however, the penis opens apically, while in Campylenchia, 

 Telamona and others it opens at or near the apex. In every case, 

 however, the opening seems to be guarded by the external membrane 

 and is constant in position within the species. The shape of the 

 apex also is constant for the species ; in fact, the whole organ seems 

 to afford an excellent specific character for use in systematic work. 

 Canon Fowler's characterization of the cedagus of Stictocephala 

 does not hold good for all the species of the genus. 



The cephalic portion of the styles and the dorsal arm of the 

 cedagus are practically internal parts. It seems as though these 

 parts have distinct layers added to them at various intervals, thus 

 adding to the length of the former and to the width of the latter 

 This may account for the variable condition seen in these organs, 

 even within the species. The terminal portions, however, seem to 

 be constant. 



The sternal plate, both as to shape and the extent of its division 

 into two parts, is an excellent and readily available character for 

 taxonomic work. It may be the ninth sternite, but the question as to 

 its possible homology with abdominal appendages at once arises. 

 At any rate, it seems to be exactly homologous with the plates of the 

 Cicadellidse. 



Further work with these genital organs will undoubtedly lead to 

 their greater use in systematic work. The writer has found that 

 specimens identified as identical can frequently be separated and 

 properly classified by a study of these organs. It is to be hoped that 

 the various genera will be studied from this standpoint in the days 

 to come. If they are the writer feels that several generic changes 

 will be made. Thus it would seem that the genus Stictocephala 

 should be divided, for the genitalia of S. festina and S. lutea cannot 

 possibly belong to members of the same genus. On the other hand, 



