PROCEEDINGS OF THE 



ENTOMOLOGICAL SOCIETY OF WASHINGTON 



VOL.24 MARCH 1922 No. 3 



A COMPARISON OF THE FIRST MAXILLAE OF APTERYGOTAN 



INSECTS AND CRUSTACEA FROM THE STANDPOINT 



OF PHYLOGENY. 



BY G. C. CRAMPTON, Ph. D., Massachusetts Agricultural College. 



The present paper dealing with the phylogenetic origin of the 

 maxillae of insects, is offered as the fourth of a series of articles 

 in which the evidence for deriving the various insectan struc- 

 tures from crustacean prototypes, has been presented in order 

 to demonstrate that the Crustacea, rather than the Chilopoda 

 or other "myriopods," are the nearest representatives of the 

 ancestors of insects. The other papers of this series were pub- 

 lished in Vol. 28 of Psyche (an article on the evolution of the 

 paragnaths or "superlinguae" of insects), in Vol. 29 of the 

 Journal of the New York Entomological Society (an article on 

 the evolution of the mandibles of insects), and in Vol. 32 of the 

 Entomological News (a paper on the evolution of the cerci of 

 insects). A general review of the subject was presented in the 

 50th Annual Report of the Entomological Society of Ontario 

 for 1919, and in the Transactions of the Entomological Society 

 of London for 1921 ; but it is only in the papers dealing with each 

 phase of the subject separately, that drawings of the anatomical 

 details were given to demonstrate the truth of the contentions 

 made, since it would not be feasible to attempt to present all of 

 the evidence, accompanied by the necessary illustrations, in a 

 single paper. 



It is manifestly disadvantageous (although unavoidably 

 necessary) to scatter the evidence through a series of discon- 

 nected papers, since in so doing, the ever increasing mass of 

 evidence loses much of its cumulative effect, and it is not so 

 readily apparent that each additional study of another struc- 

 tural feature merely adds its quota to the overwhelming 

 accumulation of facts driving one irresistibly to the conclusion 

 that the Crustacea, rather than the Chilopoda, have departed 

 the least from the type ancestral to the Insecta for in each 

 case, it has been the Crustacea alone which have furnished the 

 key to the proper interpretation of the parts in insects, and they 

 alone furnish an unbroken series of evolutionary stages connec- 

 ting the insects with the lower arthropods. On this account, 



