INSECTA OE HEXAPODA. 127 



3. Lepidoptera, or Butterflies and Moths. 



4. Diptera, or True Flies. 



5. Thysanoptera, or Thrips. 



6. Hemiptera, or Bugs and Plant Lice. 



7. Orthoptera, or Cockroaches and Grasshoppers. 



8. Neuroptera, or Lace-wing and Caddis Flies. 



9. Aptera, or Thysanura and Collembola ( = Spring-tails, &c.) 

 The first four orders undergo a complete, the next four an 



incomplete, metamorphosis. These orders may he distinguished 

 by the following characters : — 



Complete metamorphosis : — 

 Coleoptera — Two pairs of wings, first pair horny (elytra). Mandibulate. 

 Hymenoptera — Two pairs of wings, all clear, first with a dark stigma along 



the costa. Mandibulate and haustellate. 

 Lepidoptera — Two pairs of wings covered more or less with scales. 



Haustellate. 

 Diptera — One pair of wings only. Haustellate. 



Incomplete m/:tnmorphosis : — 



Thysanoptera — Four narrow fringed wings. "Weak suctorial mouth. 

 Hemiptera— 'XlTio pairs of wings, either (i) all transparent, or (ii)the first 



pair half leathery at the base and transparent at tip {hemiclytra). 



Haustellate. 

 Orthoptera — First pair of wings leathery with longitudinal veins ; second 



pair fan-shaped. Mandibulate. 

 Nexiroptera — Two pairs of lace-like wings. Mandibulate. 



Scarcely any metamorphosis : — 

 Aptera — No wings at all. Mandibulate or slightly haustellate. 



The above classification is the one now generally adopted, 

 and is followed in the excellent section on Insects by Dr Sharp 

 in ' The Cambridge K"atural History.' -^ 



' Camb. Nat. Hist., vol. v. (Peripatus, Myriapoda, and Insecta), p. 172. 



