CLASSIFICATION AND ORIGIN OF INSECTS U23 



Let me say a word as to the general insect type. 

 It may be described shortly as consisting of animals 

 possessing a head, with mouth-parts, eyes, and an- 

 tennae; a many-segmented body, with three pairs of 

 legs on the segments immediately following the head ; 

 with, when mature, either one or two pairs of wings, 

 generally with caudal appendages. 



Thus, then, we find in many of the principal 

 groups of insects that, greatly as they differ from 

 one another in their mature condition, when they 

 leave the egg they more nearly resemble the typical 

 insect type, consisting of a head, a three-segmented 

 thorax, with three pairs of legs, and a many-jointed 

 abdomen, often with anal appendages. Now, is there 

 any mature animal which answers to this description? 

 We need not have been surprised if this type, through 

 which it would appear that insects must have passed 

 so many ages since (for winged Neuroptera have 

 been found in the carboniferous strata), had long ago 

 become extinct. Yet it is not so. The interesting 

 genus Campodea still lives; it inhabits damp earth, 

 and closely resembles the larva of Chloeon, consti- 

 tuting, indeed, a type which occurs in many orders of 

 insects. It is true that the mouth-parts of Campodea 

 do not resemble either the strongly mandibulate form 

 which prevails among the larvae of Coleoptera, Or- 

 thoptera, Neuroptera, Hymenoptera, Lepidoptera; 

 or the suctorial type of the Homoptera and Heterop- 

 tera. It is, however, not the less interesting or sig- 

 nificant on that account, since its mouth-parts are in- 

 termediate between the mandibulate and haustellate 

 types ; a fact which seems to me most suggestive. 



