CLASSIFICATION 



The following diagram (Fig. 9) expresses very crudely one view as 

 to the annelid origin of the chief classes of Arthropoda. 



The naturalness of the phylum Arthropoda was questioned by 

 Kingsley and Packard. The latter author divided Arthropoda into 

 five independent phyla, holding that "there was no common ancestor 

 of the Arthropoda as a whole, and that the group is a polyphyletic one." 

 This iconoclastic view, however, by emphasizing unduly the structural 

 differences among arthropods, tends to conceal the 

 many deep-seated resemblances that exist between the 

 classes of Arthropoda. 



Carpenter, in a most sagacious summary of the 

 whole subject of arthropod relationships, brought to- 

 gether no little evidence in favor of a revised form of 

 the old Mullerian theory of crustacean origins. He 

 traced all the classes of Arthropoda back to com- 

 mon arthropodan ancestors with a definite number 

 of segments and distinctly crustacean in character; 

 then traced these primitive arthropods back to forms 

 like the nauplius larva of Crustacea, and these in turn 

 to a hypothetical form like the trochosphere larva of 

 recent polychaete annelids. 



Orders of Insects. Linnaeus arranged insects in 

 seven orders, namely, Coleoptera, Hemiptera, Lepi- 

 doptera, Neuroptera, Hymenoptera, Diptera and 

 Aptera. The wingless insects termed Aptera were 

 soon found to belong to diverse orders and the name 

 has become so ambiguous as to meet with little 



^ i FIG. 8. Aceren- 



approval. tomon doderoi. 



From theLinnaean group Hemiptera, the Orthoptera Length, 1.28 mm. 



After SILVESTRI. 



were set apart the old order Neuroptera a heteroge- 

 neous and unnatural group, was split into several distinct orders, and 

 many other changes in the classification were necessary. 



Without entering any further into the history of the subject, it is 

 sufficient to say that increasing discrimination on the part of entomolo- 

 gists has been followed by a gradual increase in the number of orders. 



Naturally, the systems of classification have grown and changed 

 considerably, keeping pace with increasing knowledge. 



Brauer (1885) made such important contributions to the subject that 

 his system, modified more or less by Packard, Comstock and others, 

 has been followed for almost forty years. 



