CHAPTER I 



THE CHARACTERISTICS OF INSECTS AND OF THEIR 

 NEAR RELATIVES 



Phylum ARTHROPODA 

 The Arthropods 



If an insect, a scorpion, a centipede, or a lobster be examined, 

 the body will be found to be composed of a series of more or less 

 similar rings or segments joined together; and some of these seg- 

 ments will be found to bear jointed legs (Fig. i) . All animals possess- 

 ing these characteristics are classed together 

 as the Arthropoda, one of the chief divisions or 

 phyla of the animal kingdom. 



A similar segmented form of body is found 



among worms; but these are distinguished 



from the Arthropoda by the absence of legs. 



tv — It should be remembered that many animals 



b^^ commonly called worms, as the tomato-worm, 



' \ ^Nr the cabbage-worm, and others, are not true 



worms, but are the larvae of insects (Fig. 2). 



The angle-worm is the most familiar example 



of a true worm. 



In the case of certain arthropods the dis- 

 tinctive characteristics of the phylum are 

 not evident from a ctirsory examination. 

 This may be due to a very generalized condi- 

 tion, as perhaps is true of Peripatus; but in 

 most instances it is due to a secondary modifi- 

 cation of form, the result of adaptation to 

 Thus the segmentation of the body may be 



Fig. I . — An arthropod. 

 Special modes of life. 



Fig. 2. — A larva of an insect. 

 (1) 



