322 W. D. FUNKHOUSER 



with success, as systematic characters (Distant, 1908 a: 31), and are very 

 distinctive in certain species. The nature and function of the deposit is 

 unknown, but its presence in many forms entirely precludes the use of 

 the scleritic structure for taxonomic purposes. This same woolly covering 

 — described by various authors in various terms but often designated as 

 " cretaceously sericeous" — is also commonly found on the exposed 

 scutellum. In fresh specimens it is generally snow-white in Color and is 

 a most attractive decoration. 



In the genus Oxyrhachis, previously mentioned, both the meso- and the 

 metapleura are extended to form short, blunt teeth. Such developments 

 are, however, rare in the family. 



A striking development of the pleura which is characteristic of the 

 Membracidae is found in the mesothoracic episternum. This is the 

 episternal hook (Plate xxxiii, 13). This hook arises from near the upper 

 anterior margin of the sclerite and projects forward, engaging the posterior 

 margin of the prouotum. It is found in the great majority of the genera 

 of the family, but not in all. Its function would appear to be the inter- 

 locking of the pro- and the mesothor^x by an external mechanical means. 

 It has been noted that internally these segments are but weakly joined, 

 the intersegmental membrane being fragile and easily torn. The shape 

 and the position of the hook vary but little, and in all cases the process is 

 close to the wing base. It seems somewhat strange that this peculiar 

 and rather conspicuous development should have escaped the notice 

 of workers on the Membracidae, but there is apparently no mention of the 

 structure in the systematic or the morphological literature of the family. 

 The fact that it is absent in certain genera, but present in most, would 

 seem to make it a valuable generic character. It has not been found 

 to vary within a genus. 



The trochantin of the metathorax is much larger than this sclerite in 

 either of the other two thoracic segments. It shows the same general 

 shape as in the other segments — an elongated wedge or triangle — but 

 is longer, wider, and thicker. It forms part of the lateral margin of the 

 coxal cavity and joins the cephalic bar of the sternum at its lateral 

 extremity. No evidence has been found of either a transverse or a longi- 

 tudinal divison of this sclerite, and nothing that would suggest the 

 " trochantinus major " and the " trochantinus minor " which Cranipton 

 (1909:26-27) has found in other ord(u-s of insects. 



