CHAPTER VI 



THE CLASS AND ORDERS OF INSECTS 



IN the course of the preceding chapters, it has been neces- 

 sary to make occasional reference to orders and other 

 classificatory groups in which the insects, whose life- 

 histories have been sketched, are arranged by systematic 

 naturalists. With the leading facts of insect structure and 

 growth thus reviewed, it seems now advisable to set forth a 

 condensed summary of these classificatory groups, so that 

 before passing on to other aspects of the subject, we may 

 take a general survey of the whole class of insects and realize 

 the varying degrees of likeness and difference that are to be 

 found among them. And in this survey, as is appropriate to 

 the subject of the book, especial attention will be paid to the 

 life-histories. 



Early in Chapter II (p. 5-6), the Insects were defined as a 

 Class of the great group or Phylum of the Arthropoda, the 

 leading structural characters of which were subsequently 

 pointed out. The jointed cuticle or exoskeleton, which forms 

 the most obvious outward feature of these animals, involves, 

 as was seen, the necessity for a series of moults throughout the 

 life-history, and here we see one of the foundation-facts 

 connected with insect transformation. In the great sub- 

 kingdom of the Arthropoda are included, together with Insects, 

 several other large classes of animals which display the same 

 general type of structure, for example, there are the CRUSTACEA 

 (water-fleas, barnacles, shrimps, lobsters, crabs) in most of 

 which two pairs of feelers are present, and limbs are borne on 

 most of the segments of the body, many of these limbs being 

 two-branched (biramous) and some of them usually having 

 gills, adapted for breathing dissolved air, closely connected 

 with them. There are the CHILOPODA (centipedes), elongate, 

 flattened creatures which resemble insects in having only one 



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