THE GLOW-WORM. 117 



took a male Glow-worm on the wing with his lamps 

 lighted. 



As to the object of the light, it is a matter of very 

 great uncertainty. The obvious solution of the pro- 

 blem is to say that the light is intended to guide the 

 male to his mate. 



I cannot of course say whether this is the case 

 or not, but I do not see that this is the sole object of 

 the light. There are plenty of night-flying insects 

 which manage to find their mates in the dark without 

 the use of any such aid, being attracted to them by 

 scent rather than sight ; and, even if the light emitted 

 by the female Glow-worm be intended for such a pur- 

 pose, that of the male cannot be of the slightest use 

 either to him or to the mate whom he is seeking. 



Moreover, not only the perfect insects, but the 

 pupae, the larvae, and even the eggs are slightly lu- 

 minous, so that in these cases the light evidently can- 

 not act as a guide. I am inclined to believe that no 

 utilitarian theory will account for this singular deve- 

 lopment of light from a living insect, and that the 

 phosphorescence was given to it for the same reason 

 that the butterfly's wing glows with many-coloured 

 plumage, and the rose is dowered with softly-tinted 

 petals and sweet perfume. 



This insect is doubly interesting to the entomolo- 

 gist. In the first place, it is a British light-producer : 

 and in the second, its life in the larval state is a very 

 valuable one to the agriculturist. It feeds on snails, 

 attacking and devouring them while still alive, their 

 shells being no protection to the luckless molluscs. 

 The structure of this larva is rather remarkable. In 



