1922] Crampton — Relationship of Hemiptera-Homoptera 39 



from a common source in "D", without postulating that Cole- 

 opterawithstyh-bearing ovipositors mated with "socially" incHned 

 Psocids to produce Hymenoptera possessed of these qualities, and 

 it is difficult to understand how Mr. Muir could have arrived at 

 such an obvious "redudio ad absurdum'^ in this matter. 



From the foregoing discussion, it is evident that it would be 

 impossible to accurately represent the lines of development of 

 the various insectan orders by means of a dichotomously branch- 

 ing tree, since such an arrangement ignores the evident interrela- 

 tionships between several orders of insects which apparently 

 have sprung from a single ancestral group, and I know of no 

 developmental law necessitating that all evolution in living 

 things shall follow a dichotomouslj^ branching path. In fact, 

 the known evidence would seem to indicate that such a method is 

 extremely rare among insects, and it is better to make a theor}^ 

 to fit the facts, than to adhere to some hj^pothesis which is not 

 in accord with most of the facts which one encounters in his 

 observations. I would therefore prefer to represent the orders 

 comprising the lines of descent of the three sections of winged 

 insects by means of cone-like figures in which the closely in- 

 terrelated orders converge to a common point of origin in each 

 section. Of these three Pterygotan sections, the higher insects 

 or Neuropteradelphia include the Neuropteroid super-order 

 (Neuroptera, Hymenoptera; Mecoptera, etc.) and the Psocoid 

 superorder (Psocids, Zoraptera, Homoptera, etc.); while the 

 intermediate insects or Orthopteradelphia include the Orthop- 

 teroid superorder (Orthoptera, Phasmids, etc.) the Blattoid 

 superorder (Blattids, Isoptera, Mantids, etc.) and the Plecopter- 

 oid superorder (Plecoptera, Embiids,, etc.); and the lower in- 

 sects or Plect'opteradelphia include the Palseodictyoptera, 

 Odonata, Ephemerida, etc. The final assignment of certain 

 aberrant orders of obscure affinities has not been definitely 

 determined, but in the main, the venation of the fore wings is in 

 agreement with the grouping of insects into superorders given 

 on page 114 of Vol. 53 of the Canadian Entomologist for 1921. 



