906 



THE ENTOMOLOGIST. 



Brood No. 



12 ... 



7 males, 



5 females. 





13 ... 



14 .., 



15 .. 



16 .., 



, ... 8 „ 

 . ... 10 „ 

 . ... 6 „ 

 No males, 



16 

 5 

 4 

 .5 







17 .. 



18 .. 



... ,, 



1 male, 



6 

 3 







Total 116 males, 



143 females. 







C. elis. 







Brood Nc 



). 1 . 



17 males, 



9 females. 





2 . 



3 . 



2 „ 



No males, 



5 

 12 





J5 



4 . 



5 . 



8 „ 



No males, 



1 



8 







6 . 



7 . 



8 . 



,, 

 ,, 

 4 males. 



13 



18 



2 





>> 



9 . 



1 male. 



1 









Total 32 males, 



69 females. 



In above experiments the resulting numerical proportion of 

 the sexes conclusively shows a control from some cause or causes 

 entirely apart from the influence of variations in nutrition. Some 

 writers, contending that sex is partly decided by the quantity or 

 quality of food available to the larva, have been too prompt in 

 claiming as proofs all incidents which seemed capable of bearing 

 such construction, ignoring the fact that the same incidents 

 would equally well support other and quite dissimilar solutions 

 of the general problem. It is not my purpose to discuss here 

 the question whether nutrition and other elements of environment 

 do in any instance determine sex, but merely to show that in some 

 cases at least sex is evidently dependent upon antecedent causes, 

 the influence of external conditions not applying. Regarding the 

 peculiarly variant numerical results in the present experiment, 

 my impression is that they are due to a cause which has been too 

 much neglected in the study of various problems regarding 

 species. In considering this incongruous set of sex ratios, it is 

 of importance to remember that each of the C. elis and C. 

 Christina females which laid one of the several sets of eggs, was 

 only in an incomplete degree representative of its species. To 

 exhibit fully the species C. Christina, very many varying indi- 

 viduals would be required. Although I have collected this 

 butterfly during seven seasons, and my collection shows several 

 hundred instances, all noticeably differing, I am not confident 

 that the entire species has been obtained. And to fully 



