LUMINOUS INSECTS. 423 



it may distract the attention of their enemies or alarm 

 them. And in the glow-worm since their light is usu- 

 ally most brilliant in the female ; in some species, if not 

 all, present only in the season when the sexes are destined 

 to meet ; and strikingly more vivid at the very moment 

 when the meeting takes place a besides the above uses, 

 it is most probably intended to conduct the sexes to 

 each other. This seems evidently the design in view in 

 those species in which, as in the common glow-worm 

 (L. noctilucd)) the females are apterous. The torch 

 which the wingless female, doomed to crawl upon the 

 grass, lights up at the approach of night, is a beacon 

 which unerringly guides the vagrant male to her " love- 

 illumined form," however obscure the place of her abode. 

 It has been objected, however, to this explanation, that 

 since both larva and pupa, as De Geer observed 1 *, and 

 the males shine as well as the females the meeting of 

 the sexes can scarcely be the object of their luminous 

 provision. But this difficulty appears to me easily sur- 

 mounted. As the light proceeds from a peculiarly or- 

 ganized substance, which probably must in part be ela- 

 borated in the larva and pupa states, there seems nothing 

 inconsistent in the fact of some light being then emitted 

 with the supposition of its being destined solely for use 

 in the perfect state : and the circumstance of the male 

 having the same luminous property, no more proves 

 that the superior brilliancy of the female is not intended 

 for conducting him to her, than the existence of nipples 

 and sometimes of milk in man proves that the breast of 

 woman is not meant for the support of her offspring. 



1 MUller in Illig. Mag. iv. 178. b iv. 49. 



