CHAPTEE III 



CHAKACTEEISTIC FEATURES OF INSECT LIFE SOCIAL INSECTS 



DEFINITION OF THE CLASS INSECTA COMPOSITION OF INSECT 



SKELETON NUMBER OF SEGMENTS NATURE OF SCLERITES 



HEAD APPENDAGES OF THE MOUTH EYES THORAX 



ENTOTHORAX LEGS WINGS ABDOMEN OR HIND BODY 



SPIRACLES SYSTEMATIC ORIENTATION. 



Insects form by far the larger part of the land animals of the 

 world ; they outnumber in species all the other terrestrial animals 

 together, while compared with the Vertebrates their numbers are 

 simply enormous. Yet they attract but little attention from the 

 ordinary observer, this being probably primarily due to the small 

 size of the individual Insect, which leads the unreflecting to treat 

 the creature as of little importance. " It can be crushed in a 

 moment " is perhaps the unformulated idea that underlies the 

 a,lmost complete neglect of knowledge concerning Insects that 

 prevails even in the educated classes of society. The largest 

 Insects scarcely exceed in bulk a mouse or a wren, while the 

 smallest are almost or quite imperceptible to the naked eye, and 

 yet the larger part of the animal matter existing on the lands of 

 the globe is in all probability locked up in the forms of Insects. 

 Taken as a whole they are the most successful of all the forms of 

 terrestrial animals. 



In the waters of the globe the predominance of Insect life 

 disappears. In the smaller collections of fresh water many 

 Insects find a home during a portion of their lives, and some few 

 contrive to pass their whole existence in such places ; but of the 

 larger bodies of fresh water they invade merely the fringes, and 

 they make only the feeblest attempt at existence in the ocean ; 

 the genus Halohates containing, so far as we know, the sole Insects 



