Wings membranous 



Fore wings parchment-like. 



178 ARTHROPODA 



abdomen. All insects have three pairs of thoracic legs and the 

 majority have one or two pairs of thoracic wings. Respiration is 

 accomplished by means of a complicated tracheal system. Insect 

 classification is based on the structure of the mouth parts and the 

 character of the development. Aldrich reported (1907) that there 

 were 640,000 named insect species. 



Classification ^ 



Metamorphosis very slight; biting mouth parts; wingless Thysanura. 



Metamorphosis incomplete. 



With biting mouth parts. 



Ephemerida. 



Plecoptera. 



Odonata. 



Isoptera. 



Corrodentia. 



fOrthoptera. 



Euplexoptera. 



Wingless Mallophaga. 



\nT II- 1 J Hemiptera. 



W ith suckmg mouth parts < „, ^ 



"^ ^ 1 hysanoptera. 



Metamorphosis complete. 



With biting mouth parts. 



Neuroptera. 



With wings membranous s Mecoptera. 



Trichoptera. 



With fore wings thickened Coleoptera. 



H7- LI- 1 J Lepidoptera. 



With suckmg mouth parts S t^- 



^ ^ IDiptera. 



With lapping or piercing and sucking mouth parts < „ 



Folsom (1922) gives a most elaborate classification of insects 

 according to food habits: Microphaga, feeders on sugars and salts, 

 with yeasts and bacteria; sarcophaga, flesh eaters; copraphaga, 

 eaters of molds and bacteria; mycetophaga, consumers of fungi; 

 necrophaga, eaters of dead animals, etc. (A flesh-eating insect 

 larva may eat 200 times its own weight in 24 hours.) In America 

 it is customary to classify the insects into 19 orders. We will 

 consider them thus, treating briefly of each order. 



Insects. Order 1. Thysanura. {Aptera). — T\vt Thysanura \n- 

 clude wingless insects with retracted mouth parts and no meta- 



^ Classification after Kellogg and Doane. 



