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 
seoment of all we find, in L. noctiluca, two small 
luminous points, more brilliant than the rest of 
the segment. The light of L. ttalica 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 hght 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 
