Chap. VIII. 
SEXUAL SELECTION. 
311 
numerous. Several entomologists concur in this view. Mr. Double- 
day, however, and some others, take an opposite view, and are con- 
vinced that they have reared from the egg and caterpillar states a 
larger proportion of males than of females. 
Besides the more active habits of the males, their earlier emerg- 
ence from the cocoon, and their frequenting in some cases more 
open stations, other causes may he assigned for an apparent or real 
difference in the proportional numbers of the sexes of Lepidop- 
tera, 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 Professor Canestrini, 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 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 largest ; and 
Professor Canestrini informs me that in Italy some breeders believe,, 
though on insufficient evidence, that in the first brood 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 consume more food and mois- 
ture; and thus they would be exposed 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 w T e are concerned with the 
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 Lasiocampa quercus 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. 
