216 GENITALIA OF MALE DIPTERA AND MECOPTERA 



The sternite of the eighth abdominal segment may also be 

 prolonged backward to form a pseudohypandrium, such as the 

 one labeled 8^ in figure 37. In the dipteron shown in figure 11, 

 the eighth sternite 8^, which forms a pseudohypandrium or 

 pseudo-subgenital valve of the male, also bears a pair of pseudo- 

 styli, ps, suggestive of the valves borne on the ninth sternite 

 (hypovalvae) or true subgenital plate of the male. The epand- 

 rium or ninth tergite situated above the genital apparatus of 

 the male, which bears the label ea in figures 27, 33, 9, 6, etc., is 

 frequently characteristic of the different insects in size, contour, 

 etc., and may offer a character of value in classification, since 

 it (like the hypandrium) is readily seen without dissecting out 

 the parts, as is usually necessary in studying the genitalia them- 

 selves. 



Behind the ninth abdominal segment, there occurs in many 

 insects an anus-bearing structure called the proctiger {pg of 

 figures 6, 7, 10, 12, 14, 18, 20, 24, 25, 26, 29, 33, 35, 37 and 38), 

 which possibly represents the united tenth and eleventh ab- 

 dominal segments, since in the mecopteron shown in figure 20, 

 and in the dipteron shown in figure 35, it bears the cerci c, which 

 are supposedly appendages of the eleventh abdominal segment. 

 At least, embryologists such as Heymons, Wheeler, and others 

 claim that the cerci are modified limbs of the eleventh abdominal 

 segment, and if the cerci arise as the limbs of the eleventh segment 

 in the embryo, there is no gainsaying the fact that they belong 

 to the eleventh segment, and the proctiger pg of figures 20, 35, 

 etc., must therefore contain the eleventh segment in its com- 

 position (as well as the tenth). I am not entirely convinced 

 that the cerci are really the limbs of the eleventh rather than of 

 the tenth abdominal segment, however, since it appears to me 

 that the basal segment (protopodite, or parapodial plate) of the 

 modified limb, whose endopodite forms the ccrcus, has been 

 mistaken for the eleventh sternite by the embryologists, as I 

 have pointed out in a paper pubHshed in Entomological News,^ 

 and it is quite possible that the cerci are the modified Hmbs of 

 the tenth instead of the eleventh abdominal segment, as they 

 appear to be in other insects which I have examined from the 



2 XXII, p. 257. 



