CLASSIFICATION 25 



larvae, wi.th eleven or twelve pairs of legs, suggest affinities with Lepidop- 

 tera and, more remotely, with the tenthredinid Hymenoptera. Mecop- 

 tera are most nearly related to Neuroptera (through the genus Nemop- 

 terd) and have also certain affinities with Diptera (Crampton). 



Trichoptera, while much like Mecoptera in structure and meta- 

 morphosis, are undoubtedly closely related to Lepidoptera; in view of 

 the extensive and deep-seated resemblances between caddis flies and 

 the most generalized moths (Micropterygidae) it must be concluded that 

 Trichoptera and Lepidoptera originated from the same stock, which 

 was doubtless neuropteroid. 



/V 



SIPHONAPTERA 

 THYSANOPTERA 



COLEOPTERA THYSANURA 



FIG. 33. Genealogical diagram of the orders of insects. 



Hymenoptera also trace their ancestry back to neuropteroid forms. 

 The most generalized hymenopterous larvae, those of saw-flies, are 

 caterpillar-like; but the most specialized larvae, as those of ants, bees, 

 wasps, and parasitic Hymenoptera, are more like maggots, in correlation 

 with their sedentary mode of life. 



Hymenoptera are often called the " highest" insects, chiefly on 

 account of their highly developed instincts and social life. From this 

 point of view, however, the termites also would rank high, though 

 structurally they belong among the more generalized insects. As a 

 matter of fact, the system of classification is based necessarily on 

 structure, and not on psychology; and structurally Hymenoptera are, 

 taking everything into consideration, less specialized than Diptera. 



In Diptera the cruciform type of larva attains its extreme degree of 



