108 



University of California Publications. [Entomology 



FIG. 45. Diagram of the venation of Psocidav Con- 

 stanis of the front wing are indicated by solid lines ; those 

 of hind wings by lettor c. Variables of front wings are 

 represented by dotted lines; those of the hind wings are 

 indicated by tlie letter v. Brackets indicate alternative 

 attachments of veins. 



differ greatly. Thus, Scudder considers the veins I have called 

 independents, to comprise all the branches reaching the margin 

 in the outer half of the wing. Redtenbacher and Brongniart 

 supposed that only the first two branches correspond with my 



independents, the 

 others being 

 branches of the 

 first posterior; 

 C o m s t o c k an d 

 Needham regard 

 the first two as 

 branches of the 

 primary, the next 

 three as independ- 

 ents, and the last 

 two as the first posterior. I believe that Scudder is right in 

 regard to this question, and think his conclusion is confirmed 

 by a comparative study such as is epitomized in Fig. 45. If 

 these two problems are correctly decided, the rest of the homol- 

 ogizing becomes a very easy matter. The accompanying 

 diagram (Fig. 45) gives the plan of the venation of both Avings 

 as made out by a comparative study of all the genera, fossil 

 and modern. 



SIALID^. 



The Sialidse possess the most primitive venation of all 

 living insects. The variation within the family is by no means 

 as great as is found in the earliest fossil insects. The specializa- 

 tion of the group appears to have been the setting of rather 

 narrow limits to the varia- 

 tion, instead of the production 

 of any special feature that 

 can be recognized. None of 

 the known Paleozoic insects 

 possesses a venation that falls 

 within the range of this fam- 

 ily, though nearly every fea- 

 ture in the venation can be duplicated in those ancient wings. 

 The character of the venation may be seen in the accom- 

 panying diagram (Fig. 46). There is evidence of a tendency 

 toward the reduction of cross veins and the development of .a 

 number of large cells in the disk. The manner in which the 



FIG. 46. Diagram of the venation of 

 Sialida\ Cross veins and the most vari- 

 able of the longitudinals are omitted. 



