40 A BOOK OF INSECTS 



be split up, so to speak, into varieties, and these in their 

 turn may become established as new species. 



Species which display a close similarity of structure 

 are grouped by systematic naturalists to form a genus. 

 Genera are combined as families in accordance with the 

 leading characteristics of their members. Families are 

 massed as orders, into which the whole class of insects is 

 divided. 



