Scudder.J 
372 
[Jan. 20 , 
the statement can be enforced by the further fact that the para- 
sitic groups, — those which are entomophagous, — are repre- 
sented, as well as many of those which in the present time show 
peculiar modes of life ; thus we have representatives of such mi- 
croscopic parasitic insects as Myrmar, strepsipterous insects have 
been discovered, the viviparity of the ancient Aphides has been 
shown probable, the special sexual forms of ants and white ants 
were as clearly marked as today, and the triungulin larva of 
Meloe has been found enclosed in amber, showing that the phe- 
nomenon of hypermetamorphism had already been developed. 
The insects of the Tertiary period, therefore, afford no such in- 
teresting series as may be found in the study of Tertiary Mam- 
malia, nor as can be found in the study of the insects themselves 
in paleozoic rocks. Nevertheless there have been pointed out a 
few interesting features which seem to stand in some measure as 
exceptions to what has been stated. Thus, in my recent work 
on our Tertiary insects* I called attention to some remarkable 
features in the fossil plant-lice of our Tertiaries, especially the 
great length and slenderness of the stigmatic cell, — a feature 
which affects the whole topography of the wing, and is found 
also in the only mesozoic plant-louse known ; but which neverthe- 
less cannot be regarded as of significant taxonomic importance, 
since it occurs equally in both the Aphidinae and Schizoneurinae, 
the two principal subfamilies of that group both today and for- 
merly. So, too, in treating in the same place of the Pentatomi- 
dae, I pointed, out that the scutellum was universally shorter in 
all our Tertiary forms, whether belonging to the subfamily of 
Cydninae or Pentatominae ; and I may further add the unpub- 
lished fact that it is a peculiarity of the Tertiary Stapliylinidae of 
this country that the antennae and legs are measurably shorter 
than in modern types ; this is most marked in cases where the 
species, living and extinct, of the same genera are compared. 
But in neither of these cases, any more than in the Aphidae, can 
we regard these peculiarities as any ground for separating the 
fossil from the recent forms as distinct groups. No doubt we 
shall some day be able to correlate these differences and point out 
their precise significance, which at present is not clear, but it is 
^Tertiary Insects of North America. Reports U. S. Geol. Surv. Terr., Vol. XIII f 
°. 1890. Fossil Insects of North America, Yol. II. 
