The Male Genitalia as Characters of Specific Value in 

 Certain Cryptocerata (Hemiptera-Heteroptera). 



The use of the male genitalia in specific determination has 

 been employed for a long time in certain groups of insects. 

 For the most part their use has been limited to those forms 

 possessing readily accessible and perfectly apparent genital 

 parts. 



It has been demonstrated in recent years, by Doctor Knight 

 in the Miridae and Crawford in the Homoptera, that a close 

 scrutiny of the male genitalia of forms superficially diflflcult 

 to separate affords a solution to hitherto perplexing problems. 



The writer published a study of the "Oviposition of the 

 Notonectse" in the Entomological News, vol. XXIX, 1918. 

 This was in no way a systematic paper and had in mind the 

 relation of form to function only. It was stated, however, 

 that the gonapophyses appeared to be specifically distinct in 

 size and shape and the suggestion was made that a study of 

 the males might be worth while. 



It was the writer's good fortune to be carrying on research 

 work in the same quarters in which Dr. Harry Knight was 

 working over his Miridae. It was upon his advice that the 

 writer undertook to discover specific characters in certain of 

 the water bugs. This undertaking was in the face of some 

 discouragements, for Kirkaldy wrote : "Great hopes were en- 

 tertained by me that the male genitalia (of Notonecta) would 

 furnish a reliable diagnostic character, but in the few species 

 (N. glauca, N. lutea, N. im^orata, and N. undvlata) of which 

 suitable material was available, these hopes have not been 

 realized." Furthermore, Mr. J. R. de la Torre Bueno ad- 

 mitted, when the problem was suggested to him, that he had 

 long had in mind such a study but that the species in the 

 genus Notonecta are most confusing. 



The writer, however, had before him the necessity of solv- 

 ing some questions of specific determination that had arisen 

 in connection with his biological work in the Corixidae. From 

 these researches came his determination to master the tax- 



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