312 W. D. FUNKHOUSER 



speculation. Poulton (1891 and 1903) has attempted to explain the mean- 

 ing of a series of forms by mimicry and protective resemblance (fig. 39); 

 Mann (1912) has noted a protective adaptation in a Brazilian membracid; 

 and various authors have called attention to the resemblance of different 

 species of Membracidae to parts of their hosts. No doubt the appearance 

 of a large number of species may be explained by such theories; many 

 more may be similarly accounted for by a liberal use of the imagination; 

 by far a larger number, however, baffle the wildest flights of fancy. It is 

 indeed hard to understand how it is possible for certain forms with wonder- 

 fully exaggerated pronotal processes to maintain their balance while 

 flying. It is equally remarkable that these processes should not be at 

 once broken off in the ordinary activities of the insect. Certainly it is 

 hard to account for such developments by natural selection, and it seems 



more reasonable to regard 

 the Membracidae as ex- 

 treme examples of ortho- 

 genesis. 



Pronotal developments 

 are, however, in spite of 

 their questionable func- 



FlG. 39. FORMS OF MEMBRACIDAE SUPPOSED TO RESEMBLE *^^^^' ^ ^^5**^" ^^ ^^^ WTltcr 



SEEDS of specific descriptions, 



(After Bastin) ^^^ ccrtaiu general struc- 



tures in connection with such developments lend themselves well to generic 

 diagnosis and are apparently constant. Some apply, at least as secondary 

 characters, to each subfamily. It may be noted in this respect that the 

 pronotum tends to develop in four principal directions — posteriorly, 

 anteriorly, dorsally, and from the humeral angles (Plate xxxii, 8-12). 

 These four great types of development may be found in various stages 

 of enlargement thruout the family, and on them are based many attempts 

 of subdivision into subfamilies, tribes, and genera. Modifications and 

 combinations of these types are of course common, and in some species it 

 is difficult to decide which type is dominant. 



By far the commonest of these types is the development posteriorly, 

 to cover the meso- and the metanotum and often the entire body of the 

 insect. This posterior extension is found in so large a proportion of the 

 forms that it appears to be a sort of foundation structure on which the 



