300 TUE nilNCIPLES OF [Paut II. 



and minnow, appear regularly to follow tlic practice, rare in the 

 animal kingdom, of polyandry; for the female while spawning is 

 always attended by two males, one on each side, and in the case 

 of the bream by three or four males. This fact is so well known, 

 that it is always recommended to stock a pond with two male 

 tenches to one female, or at least with three males to two females. 

 With the minnow, an excellent observer states that on the spawn- 

 ing-beds the males are ten times as numerous as the females; 

 when a female comes among the 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 in that situation for a time, are superseded by other two males." " 



INSECTS. 



In this class, the Lcpidoptera alone afford the means of judg- 

 ing 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. Tlie gen- 

 eral 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. The same 

 naturalist, however, informs me, that in the two yearly broods 

 of the Ailantus silk-moth (Bomhjx cyntlda)^ the males greatly 

 preponderate in the first, while in the second the two sexes arc 

 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 preponder- 

 ance of the males.^" Thus Mr. Bates," in speaking of the species, 



'5 Yarrell, ' Hist. British Fishes,' vol. i. 1836, p. 307 ; on the Ci/prinm 

 carpio, p. 331 ; on the Tinea vulyans, p. 331 ; on the Ahramh brama, p. 

 336. See, for the minnow {Leucisais phozirnis), ' Loudon's Mag. of Xat. 

 Hist.' vol. V. 1832, p. 082. 



5" Lcuckart quotes Mcinecke (Wagner, ' nandwiirtcrbuch dor Phys.' 

 B. iv. 1853, s. 775) that with Butterflies the males arc three or four 

 times as numerous as the females. 



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



