The Male Internal Genitalia. 



The genitalia of the various groups of insects are being 

 studied more and more both by the morphologist and syste- 

 matist, for it is now well known that in many groups they 

 are a very great help if not the chief means of separation and 

 classification. Along with the venation of the wing, they have 

 often furnished the chief characters for working out the sys- 

 tematic problems of many groups. Already much use has been 

 made of them as witnessed by work on the Melanopli and 

 other Orthoptera, many groups of the Lepidoptera, Coleoptera, 

 Diptera, Hymenoptera, and other orders. Knight's paper on 

 the genus Lygus is illustrative of their value in systematic 

 work. 



In the Homoptera some use has been made of the terminal 

 portion of the abdomen in classification. The importance of 

 the pygidium in the Diaspinse is now well known to all, and the 

 use of the terminal sclerites in the Cicadellidse has done much 

 to help in the differentiation of the species. As before men- 

 tioned, the pygofers, last ventral segment, and ovipositor of 

 the female, and the pygofers, last ventral segment, valve, and 

 plates of the male, have been the parts spoken of as the geni- 

 talia of this family. These are the parts that are external and 

 are thus readily observed. There are other parts of the 

 genitalia, however, which have been but little used and yet 

 which it seems are of much importance and could be readily 

 used, especially in cases where all other helps seem to fail. 

 These portions are what we have called the "internal male 

 genitalia," using the word "internal" merely to distinguish 

 them from the ordinarily used organs which we have styled 

 the "external genitalia." In reality these organs are not in- 

 ternal, being situated in an open genital chamber which is 

 the "terminal chamber" of Sharp's Pentatomid^. 



These organs have been but little used in systematic work 

 on the Cicadellidse. Johnson in his bulletin on the grape-leaf 

 hopper gives a drawing of them as he saw them in that species, 

 but evidently no attempt was made to get at their connection 

 with the abdomen and with each other. In his Hemiptera- 

 Homoptera of the British Isles, Edwards occasionally makes 



(44) 



