J. W. H. Harrison 29 



gives birth to structures such as the penis and its attendant organs 

 which, necessarily, show their internal character by displaying no signs 

 of hair or bristle development. 



Clearly, since the clasps once more migrate to the surface when the 

 insect emerges from the pupa ; nay, since they betray their presence 

 externally in a suppressed manner in the familiar tubercles of the pupal 

 genitalia, they must have retained therewith some connection of a 

 guiding nature directing them to the surface when such a passage 

 is imminent. 



Such a connection we see hinted at, in these intersexes, by noting, 

 whenever the valves appear externally, their invariable, significant, and 

 intimate attachment to the penultimate section of the female ovipositor 

 which we have indicated as representing the 9 th abdominal segment. 



But why in our insects should the valves fail to pass to their normal 

 position ? Simply because their position externally is taken up by that 

 part of the ovipositor homologous with the male 9th abdominal segment. 



As these creatures are fundamentally females, such structures as are 

 essentially female find preferential expression in the pupa and finally 

 in the imago. If the clash between the two sets of organs is slight 

 and they develop pari passu, then the second ovipositor segment and the 

 valves alike appear; if the male element however is weakened in its 

 expression, or is retarded otherwise in its appearance, then the female 

 structures, utilising this start, bar the way to the surface and, of 

 necessity, the male organs remain inside. 



This is equivalent to asserting that, if in a normal male we can induce 

 artificially the development of a mass of tissue to act as an obstruction 

 to the outward passage of the valves, then they ought to remain inside 

 as in my specimens. Such interference may be obtained by making a 

 small cicatrix at the critical point between the 9th and 10th abdominal 

 segments as in Chapman's experiments with Lymantria dispar, the 

 results of which were (minus the female structures) precisely the same 

 as those described in these hybrids. 



To return to the general characters of the third insect but little 

 remains to be said. On the left side the ostium bursae, the ductus 

 bursae, bursa copulatrix and signum are alike complete, and as in an 

 average Bistonine female. 



(5) Wing parts, PI. I, Fig. 3. Genitalia, Text-fig. 7. 



In this instance, the entire mass of the genitalia is unusually 

 crowded together. Exactly as in the preceding insects, the uncus 



