SEX RELATIONSHIPS OF INSECTS: 1868 235 



instances in your book on S. African butterflies, of males 

 in excess. I remember writing down one or 2 cases 

 which you gave me. 



Believe me 



Yours very sincerely 

 CH. DARWIN 



12. 



Feb. 21st [1868.] DOWN. 



BROMLEY. 



KENT. S.E. 

 MY DEAR MR TRIMEN 



You are always most kind in aiding me. The 

 argument of the Lasiocampa l strikes me as very good 

 but what an intricate subject it is ! I have had excellent 

 letters from Stainton and Bates. The latter is much 

 staggered. Have you ever heard or observed other 

 cases like the Lasiocampa. I think I have seen in 

 England many Butterflies pursuing one. But here comes 

 a doubt may not the same male serve more than one 

 female. I think I will write to Dr. Wallace of Col- 

 chester. 2 



in which the females are apparently the more numerous. These 

 numbers are quoted by Darwin in Descent of Man, &c. (1874), 250. 



1 Mr. Trimen has kindly given me the following note : 



' E. Blanchard (in his Metamorphoses, Mceurs et Instincts des 

 Insectes) had attributed to some special and peculiar sense the 

 power exhibited by many males among moths of discovering the 

 distant and concealed females of their respective species. I con- 

 tended that it could only be the sense of smell that was brought 

 to bear in such cases, instancing my own experience in the case of 

 the English ' Oak Eggar ' (Lasiocampa quercus), where the males 

 assembled to an empty box in my pocket which had contained 

 a virgin female on the previous day.' The observation is referred 

 k. in Descent of Man (1874), 252. See also Darwin's argument in 

 letter 15, p. 242. 



2 The experience of Dr. A. Wallace with the large silk-producing 

 moths is quoted in several places in the Descent of Man, c. 



