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2. The slight degree of specialization of tlie l\'tigonioidea in 

 almost every point. 



3. The Membracidae are only Tetigonioidea, highly specia- 

 lized as to the pronotum. 



4. The high degree of specialization of the Fulgoroidea and 

 their great dififerentiation in every way from the other super- 

 families. 



I especially mark the last heading, as Osborn, in particiUar, 

 who has so extended a knowledge of the Homoptera, emphati- 

 cally places the typical Tetigonioidea at the head of the Aiiche- 

 norhynchi. 



(c) THE OUTER FRAMEWORK OF LEAF-HOPPERS. 



Before proceeding further with this inquiry, I propose to dis- 

 cuss some part of the outer framework of the leaf-hoppers, and 

 I make no apology for doing this at some length because firstly, 

 almost every second author uses a different horismology, and 

 secondly, the only comparatively recent discussions (I have not 

 taken into consideration Spinola's extensive "Essay on the Ful- 

 goridae" which was published 66 years ago) on the value, for 

 taxonomic purposes, as a whole, of various organs in the Homo- 

 ptera. are those of Hansen and Osborn, the latter also being only 

 too brief. 



In Leaf-hoppers, the head appears to be composed of 2 main 

 sclerites, the cpicraniuui and the clyf^ciis ; at one time I thought it 

 possible that the 'frons' of authors might be really the clypeus of 

 other orders, the 'clypeus' really the labrum and the 'labniin' real- 

 ly the epipharynx. but the fact that in typical Cixiinae, there is 

 an ocellus at the apex of the 'frons' seems to dispose of this at 

 once, at least no one has ever supposed that there could be an 

 ocellus on the clypeus. The structure of the head-capsule 

 icpicranhim) is, and has always so far proved, enigmatical and 

 very little help in its elucidation is obtainable from text books 

 The horismology of Hemipterists is certainl}- not homologous 

 with that of workers in other orders. In Fulgoroidea there 

 are usually considered to be 3 conventional areas, viz : Vertex, 

 frons and genae ; (lorae and tempora being added in Tetigonioi- 

 dea.) In other insects the vertex is that part of the head which 

 is bounded anteriorly by an imaginary line when the insect is in 

 a horizontal situation, the frons being the remainder, mediolon- 

 gitudinally, as far as the clypeus ; thus the extent of the vertex is 

 purely conventional and de])ends upon the degree of declivitv 



