330 THE DESCENT OF MAN 



I cannot find tliat this has ever been done. The general 

 opinion appears to be that the sexes are nearly equal; but 

 in Italy, as I hear from Prof. Canestrini, many breeders 

 are convinced that the females are produced in excess. 

 This same naturalist, however, informs me that in the two 

 yearly broods of the Ailanthus silk-moth {Bomhyx cynthia), 

 the males greatly preponderate in the first, while in the 

 second the two sexes are nearly equal, or the females rather 

 in excess. 



In regard to Butterflies in a state of nature, several ob- 

 servers have been much struck by the apparently enormous 

 preponderance of the males." Thus Mr. Bates," in speak- 

 ing of several species, about a hundred in number, which 

 inhabit the Upper Amazons, says that the males are much 

 more numerous than the females, even in the proportion of 

 a hundred to one. In North America, Edwards, who had 

 great experience, estimates in the genus Papilio the males 

 to the females as four to. one; and Mr. Walsh, who informed 

 me of this statement, says that with P. turnus this is certainly 

 the case. Id South Africa, Mr. E. Trimen found the males 

 in excess in 19 species;" and in one of these, which swarms 

 in open places, he estimated the number of males as fifty 

 to one female. With another species, in which the males 

 are numerous in certain localities, he collected only five 

 females during seven years. In the island of Bourbon, 

 M. Maillard states that the males of one species of Papilio 

 are twenty times as numerous as the females.'" Mr. Trimen 

 informs me that as far as he has himself seen, or heard from 

 others, it is rare for the females of any butterfly to exceed 

 the males in number; but three South African species per- 

 haps offer an exception. Mr. Wallace" states that the 



'* Leuckart quotes Meinecke (Wagner, "Handworterbuoh der Phys.," B. iv., 

 1853, s. 775) that the males of Butterflies are three or four times as numerous 

 as the females. 



" "The Naturalist on the Amazons," vol. ii., 1863, pp. 228, 347. 



" Four of these cases are given by Mr. Trimen in his "Ehopalocera Africa 

 Australis. " 



" Quoted by Trimen, "Transact. Ent. Soc," vol. v. part iv., 1866, p. 330. 



's "Transact Linn. Soc," vol. ixv. p. 37. 



