6 SCIENCE PROGRESS. 



those of S. pyin and S. pavo7iia were fairly balanced. After 

 changing its last skin the larva resembles a large 5. pavonia, 

 though its parentage is three parts S. pyi-i. The perfect 

 insects, of which only six were reared, were in many respects 

 remarkable. Unlike S. pyri \k\^y were sexually dimorphic, 

 the females differing little from those of ^. emilice, while the 

 males showed a nearer approach to 5*. pyri. The females 

 were not dissected, but were probably sterile. Of the six 

 specimens, one was hermaphrodite and three others showed 

 a tendency in that direction. These four were the produce 

 of three separate females out of the five that laid living ova. 

 Standfuss draws attention to the fact that the normal oc- 

 currence of hermaphrodites in lepidoptera is given by Speyer 

 as about i in 30,000. The latter number he considers 

 rather too low than too high. There was no hermaphro- 

 ditism in any known member of the families of the progeni- 

 tors of these hybrids ; and its appearance in this proportion 

 must be, he thinks, a consequence of their exceptional origin. 

 On the other hand, he has bred more than 1000 genuine 

 hybrids without one such case occurring,^ nor was any such 

 tendency shown by a single one of the sixteen specimens of 

 .S". standftissi — a form whose origin is analogous to that of 

 the present cross-product. 



In the well-marked hermaphrodite mentioned above, the 

 distribution of sexual characters is remarkable. The shape 

 of the fore wings is rather female than male, the colouring on 

 the upper side of both is male ; on the under side, the right 

 is mosdy male and the left female. In both hind wings the 

 upper surface has the costal portion male, the remainder 

 female ; the right, which is about one-fifth larger than the 

 left, has the female area more extensive. The under 

 surface of the right or larger hind wing is female, of the 

 left mostly male. The right antenna is male in form ; the 

 left partly male and partly female. The external genital 

 organs on the right side are of a malformed male type ; on 

 the left side absent. 



1 Barrett {Lepidoptera of the British Islands, vol., ii., 1895, pp. 10, 

 11) gives some details of the cross between S?nerinthus ocellatus and S. 

 populi. These are said to be " often gynandrous ". 



