1922] Crampton — Relationship of H emiptera-H omoptera 
39 
from a common source in “D”, without postulating that Cole- 
opterawith styli-bearing ovipositors mated with “socially” inclined 
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 dichotomously 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 theory 
to fit the facts, than to adhere to some hypothesis 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 Plectopteradclphia 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. 
