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PHYLUM ARTHROPODA. 



GENERAL CHARACTERS 



Like other Arthropods ', Insects have segmented bodies, jointed 

 tegs, chitinous armature, and a ventral chain of ganglia linked 

 to a dorsal brain. Compared with Peripatus and Myriopods, 

 adult insects show concentration of the body segments, decrease 

 in the number and increase in the quality of the appendages, 

 and wings in the great majority. 



Insects are terrestrial and aerial, and rarely aquatic 

 animals ; usually winged as adults^ breathing by means of 



FIG. 172. Female cockroach 

 (P. orientalis^. 



FIG. 173. Male cockroach 

 (P. orient alts). 



trachece, and often with a metamorphosis in the course of their 

 life history. 



The body is divided into three distinct regions, head, thorax, 

 and abdomen. The head bears a pair of pre-oral antenna, 

 and three pairs of mouth appendages ; the thorax bears a pair 

 of legs on each of its three segments, and, typically, a pair of 

 wings on each of the posterior two : the abdomen has no 

 appendages, unless rudimentary modifications of these be re- 

 presented by stings, ovipositors, etc. 



First Type of Insects, Periplaneta (or Blattd]. 

 The COCKROACH 



Habits. The cockroaches in Britain are immigrants 

 from the East (P. orientalis\ or from America (P. americand). 



