302 THE PRINCIPLES OF [Part II. 



the females at the end, from the want of mates. 62 I cannot, how- 

 ever, persuade myself that these causes suffice to explain the great 

 excess of males in the cases, above given, of butterflies which are 

 extremely common in their native countries. Mr. Stainton, who 

 has paid such close attention during many years to the smaller 

 moths, informs me that when he collected them in the imago 

 state, he thought that the males were ten times as numerous as 

 the females, but that, since he has reared them on a large scale 

 from the caterpillar state, he is convinced that the females are 

 the most numerous. Several entomologists concur in this view. 

 Mr. Doubleday, however, and some others, take an opposite view, 

 and are convinced that they have reared from the egg and cater- 

 pillar states a larger proportion of males than of females. 



Besides the more active habits of the males, their earlier 

 emergence from the cocoon, and their frequenting in some cases 

 more open stations, other causes may be assigned for an apparent 

 or real difference in the proportional numbers of the sexes of 

 Lepidoptera, when captured in the imago state, and when reared 

 from the egg or caterpillar state. It is believed by many breeders 

 in Italy, as I hear from Prof. Canestrini, that the female cater- 

 pillar of the silk-moth suffers more from the recent disease than 

 the male ; and Dr. Staudinger informs me that in rearing Lepi- 

 doptera more females die in the cocoon than males. With many 

 species the female caterpillar is larger than the male, and a col- 

 lector would naturally choose the finest specimens, and thus un- 

 intentionally collect a larger number of females. Three collect- 

 ors have told me that this was their practice ; but Dr. "Wallace 

 is sure that most collectors take all the specimens which they can 

 find of the rarer kinds, which alone are worth the trouble of 

 rearing. Birds, when surrounded by caterpillars, would prob- 

 ably devour the largest ; and Prof. Canestrini informs me that in 

 Italy some breeders believe, though on insufficient evidence, that 

 in the first brood of the Ailantus 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, 



62 Quoted by Dr. Wallace in 'Proc. Eat. Soc.' 3d series, vol. v. 1867, 

 p. 487. 



