HEXAPODA. 
49 
We know as yet comparatively little about the minute 
structure of insects; the transformations and habits of the 
greater number of species have not been studied; and the 
blood-relationship of the various groups of insects is very 
imperfectly understood. If, therefore, one would learn 
something of the action of the laws that govern the life and 
development of organized beings, and at the same time ex¬ 
perience the pleasure derived from original investigation, he 
cannot find a better field than is offered by the study of in¬ 
sects. 
But it is not necessary that one should have the tastes 
and leisure required for careful scientific investigation in 
order to profit by this study. It can be made a recreation, 
a source of entertainment when we are tired, a pleasant oc¬ 
cupation for our thoughts when we walk. Any one can find 
out something new regarding insect architecture—the ways 
in which these creatures build nests for themselves or foi 
their young. It is easy to observe remarkable feats of en¬ 
gineering, examples of foresight, wonderful industry, unre¬ 
mitting care of young, tragedies, and even war and slavery. 
The abundance of insects makes it easy to study them. 
They can be found wherever man can live, and at all seasons. 
This abundance is even greater than is commonly supposed. 
The number of individuals in a single species is beyond com¬ 
putation : who can count the aphids or the scale-bugs in a 
single orchard, or the bees in a single meadow ? 
Not only are insects numerous when we regard individ¬ 
uals, but the number of species is far greater than that of 
all other animals taken together. The number of species in 
a single family is greater in several cases than the number 
of stars visible in a clear night. 
The word insect is often applied incorrectly to any mi¬ 
nute animal; and even among naturalists there is some lack 
of uniformity in its use. Some writers include under this 
term the Arachnida and Myriapoda, as well as the Six-footed 
Insects. But the great majority of entomologists restrict 
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