■4SO The Descent of Man. Pari' II. 



male!:, " she is immediiitelj' pressed clnsely hy a male on each side ; 

 "and when they have beec iii that sitiiatlou for a time, are superseded 

 " by other two males." " 



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 silli-moths might huve tept an exact record, but after 

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

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

 that the sexes are nearly equal, but in Italy, as I hear from Profe.-soi 

 Ciinestrini, many breeders are oonviooed that the females are pmduced 

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

 yearly brooils of the Ailanthus silk-moth {Bombyx cynflii<i}, the males 

 greatly preponderate in the first, whilst in the second the two sexes are 

 nearly equal, or the females rather in excess. 



In re;;aid to Butterflies in a state of nature, several observers have 

 been much struck by the apparently enormous proponderance of the 

 males." Tlius Mr. Bates," in speaking of several species, about a 

 hundred in number, which inhabit the Upper Amazons, says that the 

 males are iiiuoli more numerous than the females, e\en in the propor- 

 tion of a liundred to one. In North America, Edwards, who had great 

 experience, estimates in the genus Papilio the male.i 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, IVIr. R. 

 Trimen found the males in excess in 19 species j" and in one of these, 

 which swarms in opi n 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. Mailiard 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 butterdy to 

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

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

 Omithoptera crcasus, in the Malay archipelago, are more common and 

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



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



rol. i. 1826, p. 307 ; on the Cyprinis females. 



larpio, p. 331; oa the Tinea vulgaris, " 'The Naturalist en the Ama 



p. 331 ; on the Abramis brama, p. 20ns,' vol. ii. 18B3, p. 228, 347. 

 336. See, for the minnow (Zew- '* Four of these cases are given 



ciscus phoxin'is^, ' Loudon's Mag. of bv Mr. Trimen in his * Rhopalocera 



Nat. Hist.' voh V. 1832, p. 682. Africae Australis.' 



" Leackart quotes Meinecke '' Quoted by Trimen, ' Transact 



^Wagner, * Ilandwbrteibuch der Ent. Soc' vol. v. part iv. 1866, p. 330, 

 Phys." B. iv. 1853, s. 77,'')) that '• 'Transact. Lian. Soe.' vol. jiv, 



the Djales of liutterSic* ure three p. 37. 



