xxxii, '21] EXTO.MOUH;ICAL NEWS 135 



A Phylogenetic Study of the Venation of the Fore 



Wings of the Homoptera, Thysanoptera, Psocida, 



Zoraptera, Neuroptera, Embiida, Plecoptera 



and Hadentomoida with notes on the 



Hymenoptera and Coleoptera. 



By G. C. CRAMPTON, Ph.D., Massachusetts Agricultural 

 College, Amherst, Mass. 



(Continued from p. 104) 



From the foregoing discussion, it is clear that the evi- 

 dence of the wing venation would not be opposed to the view 

 that the Homoptera, Thysanoptera and Psocida are very 

 closely related, and that all of them approach the Zorapteron 

 type, which in turn was derived from types resembling the 

 Embiida and Plecoptera, and these lead back through forms 

 resembling the Hadentomoida, etc., to the Palaeodictyoptera. 

 In fact, the wing venation corroborates the evidence from 

 other sources very strikingly in many cases, but in other 

 cases I do not think that the wing veins offer as reliable sources 

 of information concerning the interrelationships of insects as 

 do other features of the body, such as the thoracic sclerites, 

 head and terminal abdominal structures ; and it is only when 

 its evidence is in full agreement with that from other sources 

 as well, that we are justified in giving so great a value to the 

 evidence of the wing venation as done by many students of this 

 phase of anatomy, who have made a veritable fetich of the 

 venation, seemingly regarding it as a sort of infallible Delphic 

 oracle, and paying no attention to evidences of relationship 

 furnished by other features, which in many cases offer far 

 better indications of relationship than the venation does ! 



It is apparent to anyone who has made- a study of a wide 

 range of structures from different parts of the body that no 

 one set of structures can be trusted in atiempting to trace 

 the lines of development of the different insectan orders, 

 since in one group of insects a set of structures, such as the 

 wing veins, will remain very conservative, while another set 

 of structures, such as the mouthparts, will become quite highly 

 modified. In another group, on the other hand, the mouth- 

 parts may remain very conservative, \\hile the wings become 



