ENTOMOLOGY 



The following diagram (Fig. 8) expresses very crudely one view as 

 to the annelid origin of the chief classes of Arthropoda. 



The naturalness of the phylum Arthropoda has been 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, has brought together no little evidence in 



favor of a revised form of the 

 INSECTA 



CHILOPODA 



CRUSTACEA 



ARACHNIDA 



DIPLOPODA 



ARTHROPODA 



MALACOPODA 

 ANNELIDA 



old Miillerian theory of crus- 

 tacean origins. He traces all 

 the classes of Arthropoda back 

 to common arthropodan ances- 

 tors with a definite number of 

 segments and distinctly crus- 

 tacean in character; then traces 

 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. Lin- 

 naeus arranged insects in seven 

 orders, namely, Coleoptera, 



Hemiptera, Lepidoptera, Neuroptera, Hymenoptera, Diptera and Aptera. 

 The wingless insects termed Aptera were soon found to belong to diverse 

 orders and the name has now become so ambiguous as to meet with little 

 approbation. 



From the Linnaean group Hemiptera, the Orthoptera were set apart; 

 the old order Neuroptera, a heterogeneous and unnatural group, has been 

 split into several distinct orders, and many other changes in the classifica- 

 tion have been 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, 

 until our present system has been attained. 



FIG. 8. Diagram to indicate the origin of Ar- 

 thropoda. 



