CHAPTER VII 



INSECTA 



Phylum TBOCHOZOA 



Sub-Phylum ARTICULATA 



Division ARTHROPOD A Types 



Class INSECTA . . . Blatta 



Anopheles 



Culex 



Glossina 



THE Insecta, or Hexapoda, excel all other classes in actual 

 numbers, and the number of species is estimated to be about 

 45 per cent, of the total number of species of animals. Most 

 insects are able to fly and, like the birds, their bodies are highly 

 charged with air. The young state is spent in feeding and 

 growing, usually in terrestrial conditions. Many spend this 

 part of their lives in fresh water, and a few insects are found 

 in or near the sea. Insects are usually small in size, but in 

 the tropics large members of some of the orders are found. 

 The body is divided into head, thorax, and abdomen. The 

 thorax of three segments bears the characteristic three pairs 

 of legs and typically two pairs of wings. 



The life -history in many is through a metamorphosis 

 familiar in the terms caterpillar, chrysalis, and winged or perfect 

 insect. Larva is the name given to the caterpillar and the 

 corresponding stage in other groups. A caterpillar is formed 

 in the case of butterflies and sawflies, and the same stage of 

 flies is called a maggot, and of beetles, grub. The chrysalis 

 and corresponding stages are termed pupae. It is a resting 

 stage in many, but the aquatic pupae of gnats and mosquitoes 

 and others are able to move about. Such are distinguished 



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