The Systematic Place of the Odonata. 



The orders of insects fall naturally into two 

 groups : those having incomplete metamorphosis, 

 Heterometabola, and those in which the metamor- 

 phosis is complete, Metabola. In the latter group of 

 orders there are four sharply separated stages, — egg, 

 larva, pupa and imago ; in the former the changes in- 

 cident to the period of adolescence are gradual, so that 

 the larval and pupal stages are not sharply defined. 

 The young continue active and feed from birth until the 

 final change to imago. Such growing insects are 

 called nymphs. 



They are arranged by Professor J. H. Comstock, as 

 follows : 



Heterometabola. rietabola. 



Thysanura. Neuroptera. 



Ephemerida. Mecoptera. 



Odonata. Trichoptera. 



Plecoptera. Lepidoptera. 



Isoptera. Diptera. 



Corrodentia. Siphonaptera. 



Mallophaga. Coleoptera. 



Euplexoptera. Hymenoptera. 

 Orthoptera. 

 Physopoda. 

 Hemiptera. 



Thus the Odonata or Dragonflies rank among least 

 specialized insects ; those most nearly related to the 



