1404 THE STORY OF THE UNIVERSE 



their metamorphoses, in which they resemble the 

 Orthoptera and Hemiptera. 



The Trichoptera, or Caddis worms, offer many 

 points of resemblance to the Neuroptera, while in 

 others they approach more nearly to the Lepidop- 

 tera. According to Westwood, the genus Phryganea 

 "forms the cpnnecting link between the Neuroptera 

 and Lepidoptera." 



The last of these small aberrant orders is that of 

 the Aphaniptera, constituted for the family Pulicidae. 

 In their transformations, as in many other respects, 

 they closely resemble the Diptera. Strauss Durck- 

 heim indeed said that "la puce est un diptere sans 

 ailes." Westwood, however, regards it as consti- 

 tuting a separate order. 



As indicated by the names of these orders, the 

 structure of the wings affords extremely natural and 

 convenient characters by which the various groups 

 may be distinguished from one another. The mouth- 

 parts also are very important; and, regarded from 

 this point of view, the Insecta have been divided 

 into two series the Mandibulata and Haustellata, or 

 mandibulate and suctorial groups, between which 

 the Collembola occupy an intermediate position. 

 These two series are: 



MANDIBULATA. HAUSTELLATA. 



Hymenoptera. Lepidoptera. 



Strepsiptera. Diptera. 



Coleoptera. Aphaniptera. 



Euplexoptera. Hemiptera. 



Orthoptera. Homoptera. 

 Trichoptera ? 

 Thysanoptera ? 



