G. C, CRAMPTON 215 



In the mecopteron shown in figure 25, the ninth tergite bearing 

 the label 9^, bears two lobe-like processes, the surstyli or sur- 

 gonopods, sg, which are situated above the gonopods or modified 

 genital limbs (genital styles), and in the mecopteron shown in 

 figure 26, the surgonopods or copulatory lobes sg are modified 

 to form accessory claspers in mating. In the dipteron shown 

 ill figure 32, the surgonopods sg also serve as accessory clasping 

 orgar.s, while in the dipteron shown in figure 37 the surgonopods 

 -■J are broad backward-projecting lobes which appear as though 

 i'cy might also be used as secondary claspers in mating. In 

 he dipteron shown in figure 35, the homologues of the surgon- 

 opods sg are not very large, nor are they well developed in the 

 me^v^pteron shown in figure 33 (sg). In the Lepidoptera shown 

 in figures 16 and 19, the surgonopods sg are fairlj- large, and, as 

 in the trichopteroii shown in figure 15, the surgonopods sg 

 usually occur on either side of a median backward prolongation 

 of the ninth tergite calind the tegumen in Lepidoptera (i.e. im 

 of figures 19, 16, and 15). The backward-projecting portion of 

 the ninth tergite; labeled th: in the mecopteron shown in figure 

 20; is also apparently homoL gous with the tegumen tm of the 

 Lepidoptera and Triohoptera (/gures 16 and 15), and since this 

 structure occurs in the Lepidoj. ""era, Trichoptera and Mecop- 

 tera, which are very closely relate 1 to the Diptera, it is indeed 

 surprising that few if any Dijjtera have developed a tegumen. 



In the hemipteron showri in figare 14, the ninth sternite 

 bears a pair of valves, hv, called the hypovalvae, which are back- 

 ward-projecting processes of the sternite. In the mecopteron 

 shown in figure 17, the hypovalvae hv are short, l)ut in the 

 mecopteron shown in figure 13, the hypovalvae Iw are long 

 slender processes, and the character of these valves should be 

 of value in classification, since they are typical of the species in 

 question. The backward-projecting processes hv of the ninth 

 sternite of the dipteron shown in figure 11, arc probably homol- 

 ogous with the hypovalvae of the other insects referred to al)Ove. 

 From its position l)eneath the male genital apparatus, the 

 sternum of the ninth a])dominal segment ha of figures 32, 34, 

 20, 17, etc., has been called the hy])andrium, or suV)gcnital plate 

 of the male, and it is tliis plat(^ wliicli Ixvirs the tiuc hypovalvae 

 or subgenital valves, mentioned aV)ovc, whvn these are present. 



TRANS. AM. ENT. SOC, XLVIII. 



