284 I'H^ DESCENT OF MAN. 



in this view. Mr. Doubleday, however, and some others, take an 

 opposite view, and are convinced that they have reared from the 

 eggs and caterpillars a larger proportion of males than of females. 



Besides the more active habits of the males, their earlier emergence 

 from the cocoon, and in some cases their frequenting more open 

 stations, other causes may be assigned for an ajiparent or real differ- 

 ence in the proportional numbers of the sexes of Lepidoptera, when 

 captured in the imago state, and when reared from the egg or cater- 

 pillar state. I hear from Prof. Canestrini that it is believed by many 

 breeders in Italy that the female caterpillar of the silk-moth suffers 

 more from the recent disease than the male; and Dr. Staudinger 

 informs me that in rearing Lepidoptera more females die in the 

 cocoon than males. With many species the female caterpillar is 

 larger than the male, and a collector would naturally choose the 

 finest specimens, and thus unintentionally collect a larger number of 

 females. Three collectors have told me that this was their practice; 

 but Dr. Wallace is sure that most collectors take all the speci- 

 mens which they can find of the rarer kinds, which alone are worth 

 the trouble of rearing. Birds when surrounded by caterpillars 

 would probably devour the largest; and Prof, Canestrini informs me 

 that in Italy some breeders believe, though on insufficient evidence, 

 that in the first broods of the Ailanthus silk-moth the wasps destroy 

 a larger number of the female than of the male caterpillars. Dr. 

 Wallace further remarks that female caterpillars, from being larger 

 than the males, require more time for their development and con- 

 sume more food and moisture; and thus they would be exposed 

 during a longer time to danger from ichneumons, birds, etc., and in 

 times of scarcity would perish in greater numbers. Hence it appears 

 quite possible that in a state of nature, fewer female Lepidoptera 

 may reach maturity than males; and for our special object we are 

 concerned with their relative numbers at maturity, when the sexes 

 are ready to propagate their kind. 



The manner in which the males of certain moths congregate in 

 extraordinary numbers round a single female, apparently indicates a 

 great excess of males, though this fact may perhaps be accounted 

 for by the earlier emergence of the males from their cocoons. Mr. 

 Stainton informs me that from twelve to twenty males may often be 

 seen congregated round a female Elachista rufocinerea. It is well 

 known that if a virgin Ladocampa quereus or Saturnia carpini be 

 exposed in a cage, vast numbers of males collect round her, and if 

 confined in a room will even come down the chimney to her. Mr. 

 Doubleday believes that he has seen from fifty to a hundred males of 

 both these species attracted in the course of a single day by a female 

 in confinement. In the Isle of Wight, Mr. Trimen exposed a box in 

 which a female of the Lasiocampa liad been confined on the previous 

 day, and five males soon endeavored to gain admittance. In Aus- 

 tralia, M. Verreaux, having placed the female of a small Bombyx in 

 a box in his pocket, was followed by a crowd of males, so that about 

 200 entered the house with him. * 



Mr. Doubleday has called my attention to M. Staudinger'sf list 



* Blanchard, " Metamorphoses, Moeurs des Insectes," 1868, pp; 225-226. 

 t " Lepidopteren-Doubletten Liste," Berlin, No. x, 1866. 



