NO. 14 INSECT ABDOMEN SNODGRASS 89 



has been fully described in Pteronarcys by Hagen (1877) and by 

 Smith (1917). The organ usually projects dorsally or forward from 

 the end of the epiproct, and may be grooved lengthwise on its pos- 

 terior surface. It was first described by Hagen as a " penis " in the 

 sense of being an organ for conducting the sperm from the genital 

 aperture of the male to that of the female, a function which Hagen 

 claimed to have proved by observation, and the organ has since been 

 known generally as the " sperm conveyor." In Nemoura vallicularia, 

 however, Wu (1923) observes that the supra-anal process serves 

 merely to support the ninth segment of the female during mating, 

 and Needham and Claassen (1925) describe the organ of Perlodes 

 signatus as a guide for " the large soft penis that issues from the apex 

 of the ninth segment beneath." Hagen and Smith apparently did 

 not observe the eversible penis in Pteronarcys, which has been shown 

 by Prison (1935) to be present and protractile in this genus. 



For a more extensive comparative study of the external genital 

 structures of male Plecoptera the student should consult the works 

 of Klapalek (1896), Smith (1917), Crampton (1918), Walker 

 (1922), Needham and Claassen (1925), and Prison (1935). 



ORTHOPTERA 



As this paper was orginally planned, the Orthoptera were to occupy 

 a prominent place in it, because it was supposed that, considering the 

 antiquity of the Orthoptera in hexapod chronology, the structure and 

 development of the external genital organs of the male would give 

 evidence of the nature of the primitive phallic organs of insects in 

 general. More familiarity with the subject, however, now suggests 

 that the complex phallic structures of the various orthopteroid fami- 

 lies have been evolved within the order ; there is no evidence that in 

 their origin these structures have been developed from paired penes, 

 and in their evolution certainly they have not produced an organ 

 comparable with the phallus of other insects. 



The male genitalia of Blattidae consist essentially of three phallic 

 lobes arising from the anterior wall of the genital chamber close to 

 the opening of the ejaculatory duct. Two of these lobes, or phal- 

 lomeres, are right and left with respect to the gonopore, the third is 

 ventral. In young nymphs the phallomeres are simple lobes of small 

 size, but with each ecdysis the lateral lobes increase in size and pre- 

 sent an altered or more complex structure. In the adults of some 

 forms {Blatta, Periplaneta) the right and left phallomeres (parameres 

 of Walker, 1922) become large organs subdivided into many parts 



