138 PHOSPHORIC INSECTS. 



they fly. However, both the males and females 

 of glow-worms possess the faculty of extinguish- 

 ing or emitting their light, seemingly at will. 



The light of the females is emitted from the 

 last three segments of the abdomen. On the last 

 segment of all we find, in L. noctiluca, two small 

 luminous points, more brilliant than the rest of 

 the segment, The light of L. italica is very 

 bright. Both sexes fly, and these insects are not 

 uncommon in Italy. Whilst flying through the 

 evening air they produce a very pretty effect ; at 

 first sight, the stars appear to be moving about in 

 all directions. We are told that it was formerly 

 a custom among the Italian youths to decorate 

 the hair of their mistresses with these " diamonds 

 of the night," which were probably less expensive 

 than pearl necklaces, and evidently surpassed the 

 brightness of the mineral diamond. 



We know that the light of glowworms is trans- 

 mitted to us directly from the body of the insect, 

 for it does not possess the properties of reflected 

 light. It has been remarked, that the light of L. 

 noctiluca is refracted like that of the sun or the 

 stars, when it passes from one medium to another 

 of greater or lesser density. But it has never 

 been analysed prismatically, so that we cannot say, 

 at present, whether it is possessed of any peculiar 

 properties.* 



* In 1808, Wollaston discovered what are called the dark lines 



