1919] Walker: Structure of Orthopteroid Insects 273 



the members of any of the orders, and that they may therefore 

 be of Httle phylogenetic value except in determining the primitive 

 form of the structure concerned or in deciding which forms in a 

 particular group are its most primitive members. Specialized 

 characters, when the factor of convergence can be eliminated, 

 are often of more value than primitive ones, particularly in 

 complex structures where an opportunity for detailed com- 

 parison is present. For instance, the arrangement of the 

 mouth-parts of the Diptera or the Lepidoptera is so distinctive 

 that these structures alone serve as recognition marks of these 

 orders. It is largely this feature which renders wing-venation 

 so useful in phylogenetic studies of insects, and although I 

 should not attribute the same value to the genitalia, I do claim 

 that they are of great phylogenetic importance when studied 

 in detail; and in this connection I may point out that Prof. 

 Crampton's studies of the thoracic and cervical sclerites are 

 very much more thorough than those of the genitalia. The 

 chitinous parts of the genitalia are in large measure internal 

 structures and unless their internal relations are carefully 

 investigated one is certain to be led to false deductions. 



In another recent paper by Dr. A. G. Newell ('18)^ the view 

 is held that the gonapophyses in both sexes represent three 

 pairs of serial appendages or limbs, belonging to the 8th, 9th and 

 10th abdominal segments; and an attempt is made to identify 

 these appendages in both sexes of all the orders. Although 

 a useful summary of the literature dealing with the subject 

 of insect genitalia is given, the investigation itself betrays a 

 lack of grasp of the fundamental principles involved, and the 

 facts of comparative morphology and development as given in 

 the bibliography cited appear to have been almost entirely 

 ignored. 



The material on which the present study is based was 

 obtained from various sources. For the gift or loan of speci- 

 mens, indispensable to the work, I am especially indebted 

 to the following gentlemen, to whom I take pleasure in expressing 

 my most sincere thanks: Prof. G. C. Crampton, Dr. C. Gordon 

 Hewitt, Dr. N. Banks, Dr. L. O. Howard, Mr. Thos. E. Snyder, 

 Mr. Morgan Hebard and Mr. W. Downes. 



» Newell, Anna Grace, Annals Ent. Soc. Am., Vol. XI, No. 2, pp. 109-142, 

 Pis. IV-XVI. 



