2 University of California Publications. [Entomology 



cated subject. The complexity arises from the plasticity of 

 the organ upon which its value for systematic and phyletic 

 purpose depends, — a plasticity that permits the minute differ- 

 ences between species or varieties to record themselves, thus 

 making the older history so nearly illegible that one is hardly 

 to be criticised if he despair of deciphering it. 



Aside from the color-pattern, — a matter scarcely ever of more 

 than generic value, and usually less, — the venation of the wing 

 includes practically every item that has been found useful in 

 classification based on that organ. We must turn, therefore, 

 to the study of venation for the evidence afforded by the wings 

 upon the questions of their origin and the relationship between 

 the larger groups of insects. 



The important contributions that have been made to the 

 study of venation may be put into three quite distinct groups, 

 corresponding to the motive, or point of view, of the investi- 

 gator. By far the largest number of authorities on venation 

 are the systematists, or the students of single groups, who 

 have in most cases ignored similar work by fellow laborers in 

 other groups, the result being an almost unendurable confusion 

 of nomenclature. It should be said, however, that we owe to 

 them a most careful elaboration of the details and in almost 

 every case a trustworthy establishment of homologies within 

 the groups upon which they labored. We shall here mention 

 only some of the most conspicuous authors from the almost 

 endless list of those who have studied along this line. Among 

 those most worthy of mention, on account of the quality, 

 extent, or significance of their contributions, are De Selys 

 Longchamp (Odonata); Eaton (Ephemerida?); Hagen, ^^'ood- 

 Mason (Embidse); Hagen, Kolbe, MacLaughlin, Spangberg 

 (Psocida"); Brunner von Wattenwyl (Orthoptera) ; Fieber, 

 Kolenati (Hemiptera); Heer, Kirby, Kempers (Coleoptera); 

 MacLaughlin (Phryganseida?); Low, Meigen, Schiner (Diptera); 

 Forster, Schenk, Shuckard, Thompson (Hymenoptera) ; Com- 

 stock, Packard, and Spuler (Lepidoptera). The second group 

 are the paleontologists, three of whom have made very valu- 

 able and extensive studies on the venation of the wings of 

 recent insects, as a means of laying a foundation for their 

 work on fossil forms. They are Brongniart, Heer, and Scudder. 



The most important studies of a general nature, besides 

 those of the authors just noted, are those dealing with the 



