PROPORTION OF THE SEXES. 247 



great excess of males, in the above cases of certain butterflies 

 which are extremely common in their native countries. Mr. Stain- 

 ton, who has paid very 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 more 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 eggs and cater- 

 pillars a larger proportion of males than of females. 



Besides the more active habits of the males, their earlier emerg- 

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

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

 real difference in the proportional numbers of the sdxes of Lepi- 

 doptera, when captured in the imago state, and when reared from 

 the egg or caterpillar state. I hear from Professor Canestrini, 

 that it is believed by many breeders in Italy, that the female cat- 

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

 the male; and Dr. Staudlinger 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 collect- 

 or would naturally choose the finest specimens, and thus uninten- 

 tionally 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 specimens 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 larg- 

 est; and Professor 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. Wal- 

 lace further remarks that female caterpillars, from being larger 

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

 consume more food and moisture; and thus they would be ex- 

 posed during a longer time to danger from ichneumons, birds, 

 &c., 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 indi- 

 cates 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 Blachista 



