G, C. CRAMPTON" 211 



migrate to a position on either side of the intromittent organ pv 

 (or they may be simply outgrowths on either side of the intro- 

 mittent organ), and the above-mentioned structures may become 

 involved in the formation of the intromittent organ of higher 

 insects. In some cases, I think that secondary chitinizations 

 of the body wall in the neighborhood of the opening of the 

 ejaculatory duct enter into the composition of the intromittent 

 organ, and the various secondarily formed portions of the intro- 

 mittent organ make it very difficult to interpret the parts cor- 

 rectly in certain cases, unless all of the evolutionary stages in 

 their formation can be found. In some insects, the terminal 

 portion of the ejaculatory duct forms the penis, but it is pref- 

 erable to speak of the intromittent organ simply as the aedeagus, 

 regardless of the homologies of its various parts. 



If we compare the claspers of the sawfly shown in figure 5, 

 with those of the ephemerid shown in figure 4, it would appear 

 much more prol^able that the basal segments of the claspers gs 

 of the sawfly shown in figure 5 represent the basal segments of 

 the genital styles gs of the mayfly shown in figure 4, rather than 

 that the basal segments gs of the claspers of the sawfly shown 

 in figure 5 should represent the coxites or protopodites p of the 

 ephemerid shown in figure 4 (since the l)asal plate 7? of figure 5 

 represents the united coxites p of figure 4), and the musculature 

 of the parts in ciuestion would permit of such an interpretation. 

 The two-segmented genital claspers or genital styles ex of the 

 sawfly shown in figure 8 are apparently homologous with the 

 two-segmented genital styles ex of the mecopteron shown in 

 figure 25, as I have pointed out in several papers dealing with 

 these insects; so that Muir, 1921, is evidently mistaken in 

 attempting to homologize the basal segment gs of the two- 

 segmented genital style ex of figure 25, with the coxites or pro- 

 topodites p of figure 4, instead of homologizing the basal seg- 

 ments gs of the two-segmented genital styles ex of figure 25 with 

 the basal segments gs of the two-segmented genital styles ex 

 of figure 4, as should be done. This is a very important matter, 

 since the proper interpretation of the claspers of the Diptera 

 depends upon the correct intcri)retation of the parts in the 

 Mecoptera, which approach the dipteran type remarkable closely. 



TRANS. AM. ENT. SOC, XLVIH. 



