325J LARVAE OF THE TENTHREDJNOIDEA—YUASA 



I. INTRODUCTION 



That the cardinal principle of modern taxonomy is based on the funda- 

 mental facts of evolution and that the essential problem of classification 

 is the phylogenetic relationship of organisms need no argument. In order 

 to ascertain genetic affinities, it is not sufficient to investigate the morpho- 

 logical characters alone, but all other attributes, physiological and biolog- 

 ical, must be considered. It is also evident that the immature stages of 

 organisms should receive as thoro consideration as the adult if taxonomy 

 of insects is to attain that degree of comparative perfection obtained in the 

 classification of other organisms. 



Systematic entomologists, dealing as they do with animals of such 

 diversity and complexity morphologically and biologically, have from 

 early times recognized, at least to some extent, the taxonomic significance 

 and value of the developmental stages of insects, but the practical difficul- 

 ties in obtaining necessary materials, accurately determined and adequate 

 in quantity and range, have made progress in this phase of insect taxonomy 

 very tardy. A good start, however, has been made by recent workers as 

 was pointed out by Brues (1919), and their results vindicate both the 

 possibilitity and practicability of such investigations. There is, moreover, 

 an urgent demand for such studies from economic entomologists, who are 

 constantly confronted by the problem of identifying the immature stages 

 of economic species. 



The present study is an attempt to deal with the larvae of the Ten- 

 thredinoidea from the standpoint of synoptic and, to some extent, genetic 

 classification. The systematic significance of the morphological charac- 

 ters will be discussed in part two; the taxonomic treatment of the families, 

 subfamilies, genera, and species will constitute part three; and, as full a 

 discussion of the phylogenetic relationship of the families as is possible 

 with the data at hand, will form part four. No one appreciates the inade- 

 quacy of this study, both in thoroughness and comprehensiveness, more 

 than the author, but it is hoped that he has opened a way for those who 

 will advance our knowledge of this highly interesting group of insects to 

 a more satisfactory condition in the future. 



The taxonomic literature dealing with the adults of the Tenthredinoidea 

 is extensive. The historical development of the subject is interesting to 

 students of this group of insects but a detailed account is out of place here. 

 However, a brief statement of the history of the group is desirable. 



