CHAPTER III. 
Class Hexapoda (Hex-ap'o-da). 
The Insects . 
The members of this class are air-breathing Arthropoda , 
with distinct head , thorax , and abdomen. They have one pair 
of antenna, three pairs of legs , and usually one or two pairs 
of wings in the adult state . 
There are about us on every side myriads of tiny crea¬ 
tures that are commonly passed unnoticed, and even when 
observed, they are usually thought to be unworthy of serious 
consideration. But all life is linked together in such a way 
that no part of the chain is unimportant. Frequently upon 
the action of some of these minute beings depends the mate¬ 
rial success or failure of a great commonwealth. The intro¬ 
duction and spread of a single species of insect (the Cot- 
tony-cushion Scale) in California threatened the destruction 
of the extensive orchards of that State ; thousands of trees 
perished. The introduction of a few individuals of a partic¬ 
ular kind of Lady-bug {Vedalia cardinalis ), which feeds upon 
this pest and multiplies rapidly, soon checked the evil, and 
has nearly removed the pest from the State. 
But insects are of interest to us for other reasons than 
the influence they may have upon our material welfare; the 
study of them is a fruitful field for intellectual growth. It is 
not a small matter to be able to view intelligently the facts 
presented by the insect world, to know something of what 
is going on around us. And so rich is this field that no one 
gains more than a mere smattering concerning it. 
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