PROC. ENT. SOC. WASH., VOL. 24, NO. 2, MAR., 1922 77 



Crustacea. Comparative embryology and anatomy clearly 

 show that the superlinguae of insects are the paragnaths of 

 Crustacea, and the first maxillae of insects are the first maxillae 

 of Crustacea, and the evidence of comparative anatomy and 

 embryology if further confirmed by the form and function of 

 the organs in question. 



The evidence obtained from the study of the minuter details 

 of the maxillary structures of insects substantiates that drawn 

 from other sources, indicating so close a relationship between 

 the apterygotan insects, that it would be wholly unjustifiable 

 to attempt to group the Apterygota otherwise than in a single 

 sub-class; and a study of the minute details of structure of the 

 maxillae furnishes further confirmation of the claim that the 

 Crustacea alone represent the probable types ancestral to 

 insects, and if the Crustacea are not the actual ancestors of 

 insects, they at least enable us to determine what the ancestors 

 were probably like, possessing as they do a number of features 

 unmistakably suggestive of the prototypes of many of the struc- 

 tures of insects, which are built upon the same plan, but are 

 much more highly modified in insects. 



The present paper is largely of the nature of a preliminary 

 study, in which an attempt has been made to determine the 

 true nature of the maxilla as the basis of further work along this 

 line. In the second part of this paper, it is proposed to trace 

 the various modifications of the maxilla in different insects, 

 with particular reference to the evidence it may add to that 

 from other sources, in determining the closest affinities and the 

 interrelationships of the various insectan orders. 



Appendix. 



The appended textfigures of the embryonic development of 

 the head structures of insects and Crustacea have been added 

 to show that the evidence of embryology is in full accord with 

 that of comparative anatomy (Psyche, Vol. 28, p. 84) which 

 clearly indicates that the "superlinguae" of insects represent 

 the paragnaths of Crustacea. As may be seen in Textfigure 5, 

 the superlinguae" of insects (labeled "e") are mandibulur 

 structures arising (in the embryo) upon the mandibular ganglia, 

 immediately mesal to the forming mandibles (labeled "d"); 

 while the paragnaths of a crustacean embryo (labeled "e" in 

 Textfigure 6) are likewise mandibular structures arising upon 

 the mandibular ganglia, immediately mesal to the forming 

 mandibles (labeled "d" in Textfigure 6). The evidence of 

 embryology is therefore no less conclusive than that of compara- 

 tive anatomy in demonstrating that the "superlinguae" of 

 insects are really the paragnaths of Crustacea, and it is therefore 



