Chap. VIII. Proportion of the Sexes. 2$ I 



here add, that in Hyperythva, a genus of moths, Guenee says, that 

 from four to five females are sent in collections from India for one 

 male. 



When this subject of the proportioual numbers of the sexes of insects 

 was brought •before the Entomological Society, 79 it was generally 

 admitted that the males of most Lepidoptera, in the adult or imago 

 state, are caught in greater numbers than the females : but this fact 

 was attributed by various observers to the more retiring habits of the 

 females, and to the males emerging earlier from the cocoon. This 

 latter circumstance is well known to occur with most Lepidoptera, as 

 well as with other insects. So that, as M. Per.sonnat remarks, the 

 males of the domesticated Bombyx Yamamal, are useless at the begin- 

 ning of the season, and the females at the end, from the want of 

 mates. 80 I cannot, however, persuade myself that these causes suffice to 

 explain the great excess of males, in the above cases of certain butter- 

 flies which are extremely common in their native countries. Mr. 

 Stainton, 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. Double- 

 day, however, and some others, take an opposite view, and are con- 

 vinced 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 apparent or real difference 

 in the proportional numbers of the sexes of Lepidoptera, when cap- 

 tured in the imago state, and when reared from the vgg or caterpillar 

 state. I hear from Professor 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 mure females die in the 

 cocoon than males. With many species the female caterpillar is la v ger 

 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 

 broods of the Ailanthus silk-moth, the wasps desti oy 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 qui'e possible that 



79 ' Proc. Entomolog. Soc' Feb. ' Proc. Ent. Soc.' 3rd series, vol. V 

 r.th, 1868. 1867, p. 487. 



8C Quoted by Dr. Wallace in 



