Dec, 1904.J Powell : Wings of Certain Beetles. 237 



THE DEVELOPMENT OF WINGS OF CERTAIN 



BEETLES, AND SOME STUDIES OF THE 



ORIGIN OF THE WINGS OF INSECTS. 



By p. B. Powell, 



Stanford University, Calif. 



CONTENTS. 

 Plates XI-XVII. 



I. Introduction 237 



I. The Life History of Tomiriis plastographus and of Dendroctomis valeus 238 



II. Development of the Wings 240 



1. Formation and Growth 240 



{a ) Early Stages 240 



((^) Types of Development 241 



( <: ) Evagination of the Wings 242 



{d) Formation of the Veins. (Continued in Vol. XIII.) 



2. The Tracheal System. 



(rt ) The Tracheoles. 



(Zi ) The Tracheal of the Wing. 



III. The Origin of the Wings. 



1. The Spiracles. 



2. The Position of the Spiracles and their Relation to the Wing Discs. 



IV. Conclusion. 



Methods. 



Bibliography. 



Explanation of the Figures. 



Introduction. 



The following paper contains the result of some investigations on 

 the development of the wings of certain beetles and of an attempt to 

 throw some further light on the primitive origin of the wings of 

 insects. 



This work, done in the entomological laboratory of Stanford Uni- 

 versity, was begun at the suggestion of Professor V. L. Kellogg and 

 was carried on under his supervision, and to him my heartiest thanks 

 are due for his many helpful suggestions and the great interest he has 

 taken in my work. 



That the wings of insects with a complete metamorphosis are 

 present in the larva was known as far back as the time of Malpighi 



