36 



Studies -in the Hybrid Bistoninae. 1 V 



reaching a great pitch of development much greater than in the 

 pomonaria-pilzii crosses. Both of the right directing rods are as fully 

 formed as in a normal female but those of the left side are extremely 

 feeble. The left outer rod, at its point of attachment to the terminal 

 ovipositor segment, is thread-like but dense ; as it passes anteriorly, 

 however, it becomes feebler, thinner and broader. Of the latter type 

 too is the left lower rod. 



Uncus 



Ostium 



Left member of 



second pair 



of rods 



fiight 

 rods 



Signum 



Fig. 10. 



The ostium bursae is as usual but the ductus bursae and the bursa 

 copulatrix itself are slightly shorter and somewhat distorted. The 

 signum, however, is of the ordinary arrowhead-shaped type. 



Placed centrally and a little above the ostium is a sac containing 

 a miniature set of undeveloped male valves with bristles and hairs 

 complete. Evidently they have been unable either to attain their full 



