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CHAPTER VII. 



ARTHEOPODA OE JOINTED-LIMBED ANIMALS. 



More is known of this group of animals than of those we have 

 been dealing with in the last three chapters. This is due to 

 their more pleasing and interesting, if too often injurious, habits. 

 One seldom meets with a collector of the innumerable worms, 

 whilst, on the other hand, the jointed-limbed animals have hosts 

 of devotees in all parts of the world, especially those sections of 

 them — such as the brilliant and elegant Butterflies and Moths 

 and Beetles — which make a considerable show when captured 

 and placed in a cabinet. Yet there are several of the Arthro- 

 pod groups which meet with little attention, and these particular 

 groups, although inconspicuous, are of the greatest interest and 

 importance to the agriculturist and horticulturist. 



Arthropods are invertebrate animals which are bilaterally 

 symmetrical, and which have their bodies divided up into a 

 number of rings, called segments or somites, some or all of these 

 segments bearing ventrally one or more pairs of jointed append- 

 ages. The Arthropoda have an external skeleton formed by 

 the skin becoming hardened from the deposit of a substance 

 known as chitin. All this class of invertebrates are provided 

 with a distinct alimentary canal, nervous system, and reproduc- 

 tive organs. Eespiration takes place in a variety of ways : the 

 whole body surface may be respiratory {Acarina), true pulmonary 

 sacs may be present (Araneida), or a specially modified system of 



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