PREFACE 



DURING the last forty years, much attention has been given to the 

 development of a terminology of the wing-veins of insects that 

 should be available in the descriptions of insects of all orders, and 

 that should replace the many systems that have been devised by specialists, 

 who have restricted their studies, in each case, to a single order. There has 

 resulted from these efforts the perfection of a uniform terminology, which is 

 being very generally adopted, and which will doubtless supersede the 

 many systems still in use. 



Many investigators have contributed to the attainment of this result. 

 A brief review of their more important publications on this subject is given 

 in Chapter I of this work. 



As these publications are widely scattered through various journals that 

 are to be found only in the larger libraries, most of them are inaccessible to 

 many who wish to obtain an understanding of the uniform terminology^ and 

 of the reasons that have led to its adoption. There is, therefore, a demand 

 for a comprehensive exposition of this terminolog}' , and for a statement of 

 the facts upon which it is based. It is to meet this demand that this book 

 is offered to the public. 



I undertook the preparation of this treatise upon the earnest solicitation 

 of many co-workers in entomology, and with the feeling that the great 

 amount of work, extending over a long period, that I have devoted to this 

 subject made it appropriate for me to do so. 



It is now more than thirty years since I began a special study of the 

 homologies of the wing-veins of insects, a subject in which my interest had 

 been awakened a decade before by my teacher. Dr. Hagen. 



My first effort to solve the problem was tmdertaken in the course of the 

 preparation of an article on the H>Tnenoptera published in "The Standard 

 Natural History" in 1884. Much time was devoted to the subject, but 

 without the attainment of any results that seemed worthy of incorporation 

 in that article. With our present knowledge of the subject, it is easy to see 

 how hopeless was the attempt to solve the problem by beginning with a 

 study of the highly specialized wings of the HvTtienoptera. 



A few years later I attacked the problem again ; this time by a study 

 of the wings of the Lepidoptera. This was a more fortunate starting point ; 

 and considerable progress was made. The results of these studies were 

 published in 1892 and 1893. The results obtained by further studies of the 

 wings of the Lepidoptera and by a study of the wings of the Diptera and 

 Hymenoptera were included in a text book published in 1895. 



Soon after the publication of this text book, I\Ir. J. G. Needham and I 

 began the investigation of the development of the wings of representatives 



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