ANNALS 
OW 
The Entomological Society of America 
Volume XIV TUNER 192.1 Number 2 
THE SCLERITES OF THE HEAD, AND TH 
PARTS OF CERTAIN IMMATURE AWN 
ADULT INSECTS. 
By G. C. Crampton, Ph. D. 
(Massachusetts Agricultural College, Amherst, 
Ww 
particular, are of considerable interest in making a study 
of the interrelationships and lines of descent of the different 
orders of insects; and it is of the greatest importance, in such 
a study, that we should know the correct homologies of the 
various parts, in order to determine what paths of development 
have been followed in deriving the higher types of insects 
from the lower ones. Many investigators have made the 
mistake of attempting to compare the higher types directly 
with the lowest ones without tracing the development of these 
types through a series of intermediate forms, with the result 
that the interpretations generally accepted as correct are 
frequently quite the reverse, and the true meaning of the 
different structures has not been fully grasped in many instances. 
On this account, I would devote the greater part of the following 
discussion to the consideration of such intermediate types as 
the Coleoptera, Neuroptera, etc., which serve to connect 
the lower insects with the higher ones, since it is these inter- 
mediate forms alone which can furnish us with the key to the 
proper interpretation of the modifications of the parts met 
with in the higher forms. Consideration has also been given 
to the condition found in larval insects as well, for, although 
larval insects are usually modified in adaptation to their own 
peculiar environmental conditions, they frequently retain 
the head structures in a more primitive condition than their 
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