GROUPS OF ANIMALS 



265 



water and breathe by means of gills. Lobsters and 

 crabs are of great value as food for man. Many of 

 the smaller crusta- 

 ceans form the prin- 

 cipal source of food 

 for fishes. 



The insects include 

 more species than all 

 the rest of the ani- 

 mal kingdom put to- 

 gether. It has been 

 estimated that there 

 are between 200,000 

 and 1,000,000 differ- 

 ent kinds of insects. 

 To this group belong 

 butterflies, moths, 

 flies, mosquitoes, ants, 

 bees, wasps, beetles, 

 dragon flies, grass- 

 hoppers, crickets, 

 cockroaches, plant 

 lice, bugs, etc. Here 

 also belong all the 

 caterpillars, maggots, and grubs, for they are one stage 

 in the development of insects. 



Insects have the body divided into three main regions : 

 head, thorax, and abdomen. To the thorax are attached 

 three pairs of legs, and usually two pairs of wings. 



Fig. 121. Crayfish. 



Figr. 122. Locust, a typical insect. 



