OF WASHINGTON. 187 



which is evidently the most fundamental basis of separation pre 

 sented in this suborder, there seems to be every reason to con 

 sider the Sternorhynchi as the derivative form and the Auchen- 

 orhynchi as the basal form. The position of the rostrum upon 

 the sternum, or, more properly, the coalescence of the rostrum 

 with the sternum, must certainly be considered as a more special 

 ized condition than the free form and, in fact, the derivative form, 

 the consolidation of the rostrum with sternum being the result 

 of the close approximation of beak and sternum resulting from 

 their food habits. This division includes the families Psyllidae, 

 Aphididae, Aleyrodida3, and Coccidae, and if we arrange them 

 with reference to their successive steps of departure from the 

 generalized form, or the form most nearly approaching the 

 Auchenorhynchous type, it seems to me they would be placed in 

 the order named, the Coccidae being evidently the more special 

 ized or the most extreme form, and their apparent simplicity being 

 only the degradation or reduction resulting from the habit of per 

 manent attachment to the food-plant so general in this group. 

 It is true that in each of these families w r e find extremely special 

 ized forms, but in looking at the more generalized ones of each 

 group there is no inconsistency in the idea of their developing 

 from the single primary stem. 



The other division, beginning with those forms which have the 

 most generalized condition of wing venation and body structure, 

 would commence with the Cicadidae and follow the ascending 

 order which is given in the current systems. It is true that the 

 Cicadidae are themselves a specialized group, particularly in the 

 forms possessing musical organs, but in their approach to the 

 Psyllidae in wing venation and structure of the head and thorax 

 they seem on the whole to present more generalized characters 

 than can be found in any of the other families of the Homoptera. 



The Membracidae, except in extremely specialized pronotum, 

 are easily seen to be related to the Cicadidae and naturally take 

 their position next to them. The Fulgoridae, while possessing 

 specializations of the head, are in thoracic structure and venation 

 more generalized than the remaining families, and while possess 

 ing many highly differentiated sub-groups, may very probably be 

 interposed between the preceding families and the Jassoid division. 

 The Cercopidae in development of scutellum and in texture of 

 elytra, as well as in the specialization of the tibiae, show charac 

 ters of rather high rank, and, if placed as subordinate to the Jas- 

 soidea, they must at least be considered as a branch of nearly equal 

 or parallel rank. The Jassoidea, separable into the Bythoscopidae 

 and Jassidaa proper, may, on the whole, be considered as the 

 most highly organized of the series, and as somewhat equivalent 



