CHAPTER XI 



CLASSIFICATION 



Through the preceding chapters of this account of the 

 Biology of Insects reference has necessarily been made to 

 the orders, families, genera, species into which Insects are 

 divided. The study of animals from any point of view 

 involves the use of some classification, and it may be con- 

 venient at this stage of our discussion to consider more 

 systematically than hitherto the various groups of insects. 

 The object of systematic zoology is to express those degrees 

 of likeness and difference which become apparent as the 

 creatures are compared with each other. Here we are 

 concerned with such comparisons so far as they afford 

 help in understanding the different insects' ways of life, as 

 well as the elucidation of relationship between groups which 

 is the goal of systematic study. 



At the end of Chapter I. (pp. 13-14) a concise definition 

 of the Insects as a class was given. We noticed that insects 

 form a distinct class of that great primary division or Phylum 

 of animals called the Arthropoda. Insects resemble 

 Crustacea (lobsters, shrimps, crabs, barnacles), Arachnida 

 (spiders, scorpions), Chilopoda (centipedes), and Diplopoda 

 (millipedes), in their segmented, cuticle-clad body and 

 jointed limbs. They differ from these other classes in the 

 restriction of the well- developed locomotor limbs to three 

 pairs, and usually in the possession of wings, for the great 

 majority of insects acquire the power of flight when adult. 

 Some, however, never attain to this fullness of development. 

 It might therefore be suggested to start classifying insects 

 by setting those which have wings over against those which 



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