1947] 
Early Insect Life 
69 
about thirty-five million years, and on the basis of its flora 
and fauna, is divided into three main stages, the Upper 
Namurian, Westphalian, and Stephanian. The record of 
insects is very scanty in the oldest of these ; not until the 
late Westphalian and Stephanian rocks are insect re- 
mains sufficiently abundant and preserved to give us a 
concept of the fauna. Nevertheless, three species are 
known from the Upper Namurian, at the very base of the 
Upper Carboniferous, and they constitute the earliest 
record of the insects. One of these (Erasipteron larischi 
Pruvost), from Czechoslovakia, consists of part of a wing, 
which, though incomplete, clearly belongs to a member of 
the extinct Order Protodonata, related to the Odonata. 
Another fossil ( Stygne roemeri Hand!.), from Germany, 
is a nearly complete wing with ortliopteroid features that 
place it in another extinct order, the Protortlioptera. The 
third specimen ( Metropator pusillus Handl.), from Penn- 
sylvania, is a very fragmentary wing which might have 
belonged to any one of several orders. Now this is truly 
a meagre record, but it does reveal two facts : first, insects 
with fully developed wings existed in the earliest part of 
the Upper Carboniferous Period, about 250 million years 
ago ; and second, at least two orders, widely separated 
phylogenetically, occurred at that time. We can infer 
from this record that insects must have arisen at least as 
far back as the Lower Carboniferous in order for such di- 
versity to be attained by the beginning of the Upper Car- 
boniferous. This inference becomes even more obvious, 
when we bear in mind that morphological studies have 
shown that the most generalized or primitive insects were 
wingless, like the Thysanura. Apterous species must have 
existed, therefore, even before the winged ones. 
So much for the first record of the insects. Let us now 
briefly consider the development of the class during the 
rest of the Paleozoic era. Referring again to the LTpper 
Carboniferous table (Figure 2) we find that as we go up 
through the several stages, additional orders appear, and 
there is an increase in the total number of orders. From 
the lower half of the Westphalian stage (A and B) there 
are forty species known, representing the two orders 
