1930 ] 
Geological History of Insects 
33 
seem to have increased in the number of species right up 
to the present time. 
As I bring to a close this discussion of insect paleon- 
tology, I cannot resist a feeling of curiosity as to just what 
discoveries will take place during the next few years, and 
just how much our present conception of the geological his- 
tory of the insects will have to be modified by the end of 
this next decade. I have already ventured to predict above 
that certain existing orders will some time be found in Car- 
boniferous rocks, and have demonstrated that we must 
eventually find winged insects in the Lower Carboniferous 
and probably also in the Devonian. Just how soon this dis- 
covery will be made depends upon the cooperation which 
the entomologists receive from the geologists. For the stu- 
dent of fossil insects is, on the whole, utterly dependent 
upon the geologists not only to discover but also to collect 
his specimens. It is impossible to predict whether or not 
fossil insects will be found in any one deposit ; consequently, 
their discovery can only be made by someone who is already 
occupied with the study of that particular formation from 
some geological aspect. And even when a formation is 
known to contain insects, these fossils are so scarce that 
usually it is not practical to work the beds for insects alone. 
Of course there are a few insect-bearing strata, such as the 
Wellington Shales of Kansas and the Florissant Shales of 
Colorado, which contain a sufficiently high percentage of 
insects so that an expedition of that nature is worth while. 
But these beds are exceptions. It is upon the geologist who 
is investigating some other aspect of the strata that we 
must depend for our fossils. For this reason it is particu- 
larly deplorable — and I make this statement with all due 
apologies to the few exceptions — that geologists have not 
favored us in late years with their needed cooperation. 
While recently visiting one of the larger eastern universi- 
ties, I was much astonished to find in the possession of the 
geological department a splendid wing of a Paleodictyop- 
teran, complete from the apex to the base, and showing 
every vein with gratifying clearness. The specimen was 
without locality label, and no one appeared to know just 
where it was collected ; for several years the specimen had 
been used in the elementary geology class as an example of 
