1922 ] Crampton — Relationship of Hemiptera-Homoptera 
35 
The tacts brought out in the foregoing discussion would 
indicate that the ancestors of the Hemiptera-Homoptera arose 
from forms anatomically intermediate between the ancestors 
of the Psocids and those of the Neuropteroid insects. In other 
words, the ancestors of the Hemiptera-Homoptera were apparent- 
ly anatomically intermediate between the insects forming the 
common Protorthopteron-Protoblattid stem and the Megasecop- 
tera, and their line of descent either merged with that of the 
Protorthopteron-Protoblattid stem and the Megasecoptera, or 
paralleled them extremely closely, as they all approached their 
common origin in an ancestral group resembling the Palseodicty- 
optera in many respects. The interrelationships of the primitive 
forms grouped about the base of the lines of descent of the 
Homoptera and the Neuropteroid insects is shown in the ap- 
pended diagram (Text figure 1) in which the lines of descent in 
question are represented as though branching off in different 
directions, since this method apparently is more in accord with 
the facts of a complicated interrelationship between these 
groups of insects than is the case when one attempts to represent 
their lines of descent by means of a dichotymously branching 
tree. 
Having repeatedly stated that no living forms can be derived 
from other living forms (see footnote to page 148 of the American 
Naturalist, Vol. LIII, 1919, etc.) and since this fact is so widely 
accepted as to be more of the nature of a truism, it hardly seemed 
necessary to waste energy and space by repeating this utterly 
obvious fact every time a living insect was compared with a 
