AUTHOR S ABSTRACT OF THIS PAPER ISSUED 

 BT THE BIBLIOGRAPHIC SERVICE, JANUARY 19 



THE ANATOMY OF THE HEAD AND MOUTH-PARTS 

 OF ORTHOPTERA AND EUPLEXOPTERA^ 



HACHIRO YUASA 



ONE HUNDRED AND SIXTY-THREE FIGURES (NINE PLATES) 



CONTENTS 



Introduction 251 



Material and methods 253 



Observations 253 



A. Fixed parts of the head 253 



B. Movable parts of the head 264 



Summary 284 



INTRODUCTION 



Huxley (78), with good reasons, turned to the generalized 

 Orthoptera for a type for study and description as a representa- 

 tive of the class Hexapoda. Blatta orientalis was selected for 

 this purpose, and its anatomy received a careful consideration. 

 A few years later, Packard ('83) discussed rather briefly the ho- 

 mology of the head and mouth-parts of orthopterous and other 

 insects. Miall and Denny ('86), three years later, published a 

 book on the morphology and biology of the cockroach which is 

 still considered a classic. The descriptive and theoretical as- 

 pects of the skeleton of the head of the more generalized insects, 

 including the tentorium, were thoroughly studied by Comstock 

 and Kochi ('02). After defining the sclerites and areas of the 

 head -capsule, these writers attempted to ascribe each sclerite and 

 appendage to some one of the seven primordial segments of which 

 an insect's head was supposed to be composed. Riley ('04), who 

 investigated the embryological development of the skeleton of 

 the head of Blatta germanica, came to the conclusion that ''so 



1 Contributions from the Entomological Laboratories of the University of 

 Illinois, no. 55. 



251 



