1922 ] Crampion — Relationship of Hemiptera-Homoptera 31 
between the first branch of radius and the anterior margin of the 
wing, as well as a tendency for Rs to turn forward toward the 
anterior margin of the wing. In order to make the series include 
as wide a range of types as possible, I have included some of the 
most specialized types as well, and, as one may see by com- 
paring Figs. 17 and 19, in which radius and media are practically 
the only veins retained in a well develped condition, there is 
a marked parallelism in the more highly specialized members 
of the two groups, as well as in the intermediate and more 
primitive representatives of the Psocicls and Homotera. This 
parallelism in a wide range of wing types, as well as in a multitude 
of structures from all parts of the body, can be explained only 
as the result of the operation of the same developmental ten- 
dencies (i.e. the expression of the presence of the same genes, 
determinants or factors — -albeit these are modified to some extent 
in the derived groups by the influence of other factors) inherited 
from a common ancestry. 
From the foregoing facts, I would conclude that the Psccids 
and Hemiptera-Homoptera were descended from very similar 
ancestors, and since the Psocids were apparently descended from 
ancestors closely resembling the Protorthoptera in many res- 
pects, it naturally follows that the ancestors of the Homoptera 
must also have resembled the Protorthoptera in many respects. 
The fact that the saltatorial Orthoptera, which are the modern 
representatives of the Protorthoptera, have likewise retained 
many features suggestive of affinities with the Hemiptera- 
Homoptera is also in harmony with such a derivation of the 
Homoptera; but there are other factors involved, which further 
complicate the question of the origin of the Homoptera. The 
primitive type of venation exhibited by the fore wing of the 
Homopteron Hotinus sp., figured by Handlirsch, 1909, appears 
to be of a lower type than that of most Protorthopterous fore 
wings, and suggests affinities with the Neuroptera and Proto- 
blatticls. The venation of the Homopteron Ormenis is also very 
suggestive of that of certain Neuroptera such as Psychopsis, 
particularly in the peculiar arrangement of certain small cross 
veins which unite end-to-end to form a paramarginal line extend- 
