P-Xj'ki 



THE ENTOMOLOGIST. 



Vol. XXVI.] 



JULY, 1893. 



[No. 362. 



SEX RATIOS IN BUTTERFLIES, AND AN INFERENCE. 

 By Thomas E. Bean. 



Much has been said for and against the proposition that in 

 general more male than female butterflies are produced. As a 

 contribution to that discussion I present below the results in a 

 pretty extensive breeding of Colias Christina and C. elis. Each 

 brood mentioned is a family raised from eggs of one female. 

 This experiment was conducted very carefully, the object being 

 to ascertain the variational capacity of the two species and their 

 degree of alliance to other closely related forms. C. Christina 

 was fed on Hedysarum horeale, var. albiflorum, C. elis on Astra- 

 galus alp'mus, special care being taken to avoid introduction of 

 a stray larva, and also to keep the several families strictly 

 separate. The broods of C elis were numbered 1 to 9 inclusive, 

 those of G. Christina 1 to J 8 inclusive (omitting number 4). All 

 the families tvere subject to uniform treatment and conditions. 

 The eggs were laid during July and August, 1890, the larvae, 

 wintered under a deep shelter of snow, resuming active life in 

 May, 1891. 



The butterflies came from pupa in June and July, the pro- 

 portion of males and females being as follows : — 



No. 1 . 





2 





3 . 





5 





6 





7 





8 





9 



\ 



„ 10 



.. ^ 



11 



... 1 



G. Christina. 







7 males. 



11 females. 



1 male, 



2 





5 males, 



18 





19 . „ 



31 





17 „ 



10 





5 „ 



5 





5 „ 



3 





1 male, 



9 





16 males. 



8 





13 



ENTOM. — JULY, 1893. 



