318 W. D. FUNKHOUSER 



shows a wide range of shapes and positions (Plate xxxiii, 4). As has been 

 noted, this difference has long served as a point of distinction between the 

 subfamily Centrotinae and the other subfamilies. While this is a valuable 

 and reliable character, it is unfortunate that it must be chosen as a primary 

 distinctive structure of so large a group as a subfamily, since its determina- 

 tion often necessitates the destruction of the specimen. 



The mesonotum usually shows three rather distinct areas, but these 

 areas are apparently not separate sclerites since from the earliest nymphal 

 forms they are evidently fused. In the adult, however, the regions are 

 set off from one another by infoldings, or grooves, which may warrant the 

 application of the usual names to these parts. The scutum is uniformly 

 smooth, poorly developed, and weakly chitinized. Being covered by the 

 pronotum it is not in reality an external sclerite at all and is not functional 

 as far as protection is concerned. The scutellum when present forms the 

 second region of the mesonotum, and, as has been noted often, develops 

 to form a thick, heavy process; when undeveloped the scutellar region is 

 indicated by a mere transverse fold. Both scutum and scutellum are 

 often entirely membranous. Posterior to the scutellum is a third area, 

 separated from the scutellum by a narrow band of connective tissue. This 

 'is probably homologous with the 'pseudonotwn as described by Snodgrass 

 (1909:522-523). Snodgrass has found (page 561 of reference cited) 

 that in certain Hemiptera the mesopseudonotum is absent; but this 

 judgment is based on the study of Heteroptera only, and the Membracidae 

 are apparently representative of a different type of notal structure. In 

 the more distinct forms this pseudonotum, or postnotum, is connected 

 to the scutellum by one or more chitinized bridges (Plate xxxiii, 3), 

 breaking the connecting membrane up into a series of lacunae. In two 

 subfamilies, the Membracinae and the Darninae, an indication of a yost- 

 phragjtia is found. This appears as an extra fold of the mesonotum, 

 posterior to the pseudonotum, submembranous and irregular but of con- 

 siderable size and fairly constant. Only one icing process is found, this 

 being the posterior. The anterior process is barely indicated in a few 

 forms by a thickening or doubling of the lateral margin of the scutum 

 at its extreme ventro-caudal angle. 



The pleuron of the mesothorax is more or less turned under the lateral 

 margin of the notum, forming part of the ventral body wall. The position 

 of the sclerites if they were spread out in one plane is diagrammatically 



