G. C. CRAMPTON 213 



abdominal sternite. Metcalf apparently regards the basal 

 segments of the genital styles of the ninth al^dominal segment 

 as the sternite of the tenth segment, and consequently interprets 

 the second (terminal) segment of the genital styles as the ap- 

 pendages of the tenth abdominal segment. This very confusing 

 mix-up will undoubtedly throw anyone not conversant with the 

 true state of affairs completely off the track, and the confusion 

 is by no means lessened by the fact that Snodgrass (who is 

 usually one of the most careful and dependable of investigators) 

 has promulgated the idea that the basal segment of the genital 

 styles of Diptera represent the pleural plates of the ninth seg- 

 ment. Their origin in lower insects very clearh' shows that the 

 styli are originally ventral structures borne on the sternite of 

 the ninth segment, and a comparison of the basal segments gs 

 of the genital styles of the Mecoptera shown in figures 31 and 

 34, with the basal segments gs of the genital stjdes of the Dip- 

 teron shown in figure 32, clearly indicates the process by which 

 the basal segments gs of the genital styles, which are ventral in 

 lower insects (figure 4), may become secondarih^ crowded into 

 the lateral region of the segment as in figure 32 (gs), since in 

 figure 34, the basal segment gs is somewhat lateral in position, 

 while in figure 31 it becomes pronouncedly so, and thus anti- 

 cipates the condition exhibited by the dipteron shown in figure 

 32. 



It is a very difficult problem to decide what terms to apply to 

 the basal and distal segments of the genital styles of the ninth 

 abdominal segment. The basal segment gs of figure 8 has been 

 called the gonostipes in male sawflies, and the distal segment 

 has been variously termed the cochliarium, harpes, parameres, 

 etc., in these insects. The designation harpes and harpagones 

 has also been variously applied by lepidopterists to the fused 

 segments of the entire genital styles (or to various other parts 

 as well), and the dipterists have further complicated the con- 

 fusion by applying these terms to still other structures, so that 

 it is impossible to apply these terms in the orders in question 

 without creating confusion. While I prefer the designation gono- 

 stipes for the basal segment gs of the genital styles, and the 

 designation harpes or parameres for the distal segment h of the 



TRANS. AM. EXT. SOC, XLVIIl. 



