t$o The Descent of Man. Part II, 



males, "she is immediately pressed closely by a male on each side; 

 "and when they have been in that situation for a time, are superseded 

 " by other two males." 73 



INSECTS. 



In this great Class, the Lepidoptera almost alone afford means for 

 judging of the proportional numbers of the sexes ; for they have been 

 collected with special care by many good observers, and have been 

 largely bred from the egg or caterpillar state. I had hoped that some 

 breeders of silk-moths might have kept an exact record, but after 

 writing to France and Italy, and consulting various treatises, I cannot 

 find that this has ever been done. The general opinion appears to be 

 that the sexes are nearly equal, but in Italy, as I hear from Professor 

 Canestrini, many breeders are convinced that the females are produced 

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

 yearly brooils of the Ailanthus silk-moth (Bombi/x eynthia), the males 

 greatly preponderate in the first, whilst 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 observers have 

 been much struck by the apparently enormous preponderance of the 

 males. 74 Thus Mr. Bates, 75 in speaking 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 propor- 

 tion 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. In South Africa, Mr. R. 

 Trim en found the males in excess in 19 species ; 7fi 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, lie 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. 77 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 78 states that the females of 

 Ornithoptera croems, in the Malay archipelago, are more common and 

 more easily caught than the males ; but this is a rare butterfly. I may 



73 Yarrell, ' Hist. British Fishes,' or four times as numerous as the 

 vol. i. 1826, p. 307 ; on the Cyprhvs females. 



carpio, p. 331; on the Tinea vulgaris, 75 'The Naturalist en the Ama 



p. 331 ; on the Abramis brarna, p. zons,' vol. ii. 1863, p. 228, 347. 

 336. See, for the minnow {Leu- 76 Four of these cases are given 



ciscus phoxinus), ' Loudon's Mag. of bv Mr. Trimen in his ' Rhopalocera 



Nat. Hist.' vol. v. 1832, p. 682. Africa Australis.' 



74 Leuckart quotes Meinecke * 7 Quoted by Trimen, ' Transact 

 {Wagner, 'Handwbrterbuch der Ent. Soc' vol. v. part iv. 1866, p. 330, 

 Phys.' B. iv. 1853, s. 775) that 78 ' Transact. Linn. Soc.' vol. ixv. 

 tke males of ButterfJics are three p. 37. 



