CLASSIFICATION OF INSECTS. 171 



four classes, founded on the mode of metamor- 

 phosis ; that is, on the degree of similarity which 

 the larva and pupa states bear to the perfect state : 

 as in the preceding higher division, three of these 

 are double classes, and one is a single class. Insects 

 are termed amorphous (amorpha), in which there 

 is no resemblance between the pupa and imago ; 

 necromorphous (necromorpha), in which there is 

 a similarity, though imperfect ; isomorphous (iso- 

 morphd), in which the similarity is complete ; and 

 anisomorphous (anisomorpha), in which there is 

 great variation of metamorphosis, although a 

 general similarity of structure in the perfect state. 



632. The winged insects are also divided into 

 seven classes : the amorphous insects comprise 

 two of these minor classes, called lepidoptera and 

 diptera ; the necromorphous insects comprise two 

 classes, hymenoptera and coleoptera ; the isomor- 

 phous insects comprise two classes, orthoptera and 

 hemiptera ; and the anisomorphous insects have 

 only a single class, neuroptera. 



633. It is of great importance to adhere to some 

 fixed nomenclature of divisions, and to understand 

 the various steps as we mount from species to 

 kingdoms. To recapitulate, they are these : 

 1. Species; 2. Genus; 3. Family; 4. Order; 

 5. Stirpes ; 6. Class; 7. Tribe; 8. Province; 

 9. Kingdom : and be it recollected, the number of 

 the minor groups constituting a major group, need 

 make no variation in the name of either group. 



