242 SYSTEMATIC ZOOLOGY. 



These two classifications do not agree, as can be seen 

 from the following tables: 



MANDIBULAT^E. HAUSTELLAT^E. 



Thysanura. Hymenoptera.* 



Orthoptera. Hemiptera. 



Pseudoneuroptera. Lepidoptera. 



Neuroptera. Diptera. 

 Coleoptera. 



AMETABOLA. HEMIMETABOLA. HOLOMETABOLA. 

 Thysanura. Orthoptera. Coleoptera. 



Pseudoneuroptera. Neuroptera. 

 Hemiptera. Hymenoptera. 



Lepidoptera. 

 Diptera. 



A word may be added concerning this metamorphosis. 

 The holometabolous condition has doubtless been intro- 

 duced in order to allow the larva to retain its shape as 

 long as possible, and the changes, which are gradual in 

 the hemimetabolous group, are here condensed into the 

 last two molts. Hence the pupal condition is one of 

 great change, and consequently it would be inconvenient, 

 if not impossible, for the animal to feed at this time. 

 So the stage here becomes one of rest, so far as externals 

 are concerned. 



As will be seen from the foregoing tables, the group of 

 Hexapoda, or Insecta, is subdivided into nine groups or 

 orders, f 



* The Hymenoptera have the mouth-parts adapted for both 

 biting and sucking. 



f Many authorities recognize more orders than these, the differ- 

 ence chiefly lying in the extent to which the Neuroptera and Pseu- 

 doneuroptera are subdivided. 



