2 TERTIARY RHYNCHOPHOROUS COLEOPTERA. 
marked as to-day, and the triungulin larva of Meloe has been found in- 
closed in amber, showing that the phenomenon of hypermetamorphism had 
already been developed. 
The insects of the Tertiary period, therefore, afford no such interesting 
series as may be found in the study of Tertiary mammalia, nor as can be 
found in the study of the insects themselves in Paleozoic rocks. Never- 
theless, a few interesting features have been pointed out 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 remarka- 
ble features in the fossil plant-lice of our Tertiaries, especially the great 
a feature which affects the 
length and slenderness of the stigmatic cell 
whole topography of the wing, and is found also in the only Mesozoic plant-. 
louse known, but which, nevertheless, can not be regarded as of significant 
taxonomic importance, since it occurs equally in both the Aphidinz and 
Schizoneurinze, the two principal subfamilies of that group, both to-day and 
formerly. So, too, in treating in the same place of the Pentatomide, I 
pointed out that the scutellum was universally shorter in all our Tertiary 
forms, whether belonging to the subfamily of Cydninz or Pentatominz. I 
may further add the unpublished fact that it is a peculiarity of the Tertiary 
Staphylinidee of this country that the antennz and legs are measurably 
shorter than in modern types; this is most marked in cases where the living 
and extinct species of the same genera are compared. But in neither of 
these cases, any more than in the Aphidee, can we regard these peculiari- 
ties 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 certain that they do not afford ground for maintaining that we are here 
dealing with extinct groups any higher than genera, or, at most, than tribes. 
Yet in one or two instances extinct groups of a higher grade may 
be found. Thus, in the work already alluded to, and previously, I have 
drawn attention to a strange type of fossil Thysanura—Planocephalus— 
for which it seemed necessary to frame a new suborder, and, though its 
1 Tertiary Insects of North America, Reports U. S. Geological Survey of the Territories, Vol. x11. 
4°, 1890. 
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