CLASSIFICATION AND ORIGIN OF INSECTS 1405 



Again and this is the most important from my 

 present point of view insects have sometimes been 

 divided into two other series, according to the nature 

 of their metamorphoses: "Heteromorpha," to use 

 the terminology of Prof. Westwood, "or those in 

 which there is no resemblance between the parent 

 and the offspring; and Homomorpha, or those in 

 which the larva resembles the imago, except in the 

 absence of wings. In the former the larva is gen- 

 erally worm-like, of a soft and fleshy consistence, and 

 furnished with a mouth, and often with six short 

 legs attached in pairs to the three segments suc- 

 ceeding the head. In the Homomorpha, including 

 the Orthoptera, Hemiptera, Homoptera, and cer- 

 tain Neuroptera, the body, legs, and antennae are 

 nearly similar in their form to those of the perfect 

 insect, but the wings are wanting." 



HETEROMORPHA. HOMOMORPHA. 



Hymenoptera. Euplexoptera. 



Strepsiptera. Orthoptera. 



Coleoptera. Hemiptera. 



Trichoptera. Homoptera. 



Diptera. Thysanoptera. 

 Aphaniptera. 

 Lepidoptera. 



Neuroptera. 



But though the Homomorphic insects do not pass 

 through such striking changes of form as the Het- 

 eromorphic, and are active throughout life, still it 

 was until within the last few years generally (though 

 erroneously) considered, that in them, as in the Het- 

 eromorpha, the life fell into four distinct periods; 



