4-5 LUMliNOUS l^SDCTS. 



if we consider the infinite numbers that in certain cli- 

 mates and situations present themselves every where in 

 the night, it may distract the attention of their enemies 

 or alarm them. And in the glow-worm — since their 

 light is usually 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 ^ — 

 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. nociiluca, L.), 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, how- 

 ever, to this explanation, that — since both larva and 

 pupa, as De Geer observed'', 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 surmounted. 

 As the light proceeds from a peculiarly organized sub» 

 stance, which probably must in part be elaborated in 

 the larva and pupa states, there seems nothing incon- 

 sistent 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 



" Miiller in Illig. Mag. iv. ITS, " iv. 49. 



