6 ON THE ORIGIN AND [CHAP. 



HETEROMORPHA. HOMOMORPHA. 



Hymenoptera. Euplexoptera. 



Strepsiptera. Orthoptera. 



Coleoptera. Hemiplera. 



Trichoptera. Homoptera. 



Diptera. Thysanoptera. 

 Aphaniptera. 

 Lepidoptera. 



Neuroptera. 



But though the Homomorphic insects do not pass 

 through such striking changes of form as the 

 Heteramorphic, and are active throughout life, still 

 it was until within the last few years generally 

 (though erroneously) considered, that in them, as 

 in the Heteromorpha, the life fell into four distinct 

 periods ; those of (i) the egg, (2) the larva, charac- 

 terized by the absence of wings, (3) the pupa with 

 imperfect wings, and (4) the imago, or perfect insect. 



I have, however, elsewhere l shown that there are 

 not, as a matter of fact, four well-marked stages, and 

 four only, but that in many cases the process is much 

 more gradual. 



The species belonging to the order Hymenoptera 

 are among the most interesting of insects. To this 

 order belong the gallflies, the sawflies, the ichneu- 

 mons, and, above all, the ants and bees. We are 

 accustomed to class the Anthropoid apes next to 

 man in the scale of creation, but if we were to judge 

 animals by their works, the chimpanzee and the 

 gorilla must certainly give place to the bee and 

 the ant. The larvae of the sawflies, which live on 

 leaves, and of the Siricidae or long-tailed wasps, 

 which feed on wood, are very much like caterpillars, 

 1 Linnean Transactions, 1863 "On the Development of Chloeon." 



