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 Miride and Crawford in the Homoptera, that a close 
scrutiny of the male genitalia of forms superficially difficult 
to separate affords a solution to hitherto perplexing problems. 
The writer published a study of the “Oviposition of the 
Notonecte” in the Entomological News, vol. »,O.8 Deals Ms 
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 Miride. 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. wrrorata, and N. undulata) 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 Corixide. From 
these researches came his determination to master the tax- 
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