JUNE. 
205 
more familiar with them. Even now, if I see one suddenly, 
without having expected it, the impression momentarily re- 
curs. They more frequently give out the light while flying, 
than when crawling or resting, though we may often observe 
the intermittent gleam as one crawls up a stalk of grass, or 
rests on the leaf of a tree. They fly slowly, and as they 
fly, emit and conceal their light with great regularity at in- 
tervals of two or three seconds : making interrupted lines of 
light through the air, gleaming slowly along for about a yard> 
then suddenly quenched, and appearing again at the same 
distance a-head. The insect is a pretty beetle, with soft 
elytra, of a light brown colour, marked with red, and hand- 
somely striped : the light proceeds from the last three seg- 
ments of the abdomen, which are of a delicate cream colour 
by day. At night these three segments are bright at all 
times, but at the regular intervals I have mentioned, they 
flash out with dazzling splendour. If this part be plucked 
off and crushed, many patches of brilliance occur for a few 
moments among the flesh, but they gradually die away. In 
summer evenings, they often occur in great numbers, espe- 
cially over wet and marshy ground : I have seen the whole 
air, for a few yards above the surface of a large field, com- 
pletely filled with them, thicker than the stars on a winter 
night ; and, flashing and disappearing, every one moving 
about in their mazy evolutions, it is really a very beautiful 
sight : it is commonly believed these numbers precede rain. 
Notwithstanding their abundance, they are not often seen 
by day. They are usually known here by the name of light- 
ning bugs. 
C. — What can be the use of their light ? 
F. — That it has some end useful in their economy may 
not be doubted ; but what that end is, we are entirely ignorant. 
It has been concluded and taken for granted that in a parallel 
case, that of the common Glowworm of England ( Lamppns 
