LUMINOUS INSECTS. 411 
being the sexes of the same insect. In the course of 
our inquiries you will find that sexual differences even 
more extraordinary exist in the insect world. 
It has been supposed by many that the males of the 
different species of Lampyris do not possess the property 
of giving out any light; but it is now ascertained that 
this supposition is inaccurate, though their light is much 
less viyid than that of the female. Ray first pointed 
out this fact with respect to LZ. noctiluca*. Geoffroy 
also observed that the male of this species has four 
small luminous points, two on each of the two last seg- 
ments of the belly®: and his observation has been re- 
cently confirmed by Miller. This last entomologist, 
indeed, saw only two shining spots; but from the in- 
sect’s having the power of withdrawing them out of sight 
so that not the smallest trace of light remains, he thinks 
it is not improbable that at times two other points still 
smaller may be exhibited, as Geoffroy has described. 
In the males of Z. Splendidula and of L. hemiptera the 
light is very distinct, and may be seen in the former 
while flying*.—The females have the same faculty of 
extinguishing or concealing their light—a very necessary 
provision to guard them from the attacks of nocturnal 
birds: Mr. White even thinks that they regularly put it 
out between eleven and twelve every night‘: and they 
have also the power of rendering it for a while more 
vivid than ordinary. 
Authors who have noticed the luminous parts of the 
common female glow-worm, having usually contented 
themselves with stating that the light issues from the 
4 Hist. Ins. 81.» Hist. abreg. i. 168.“ Illiger Mag. iv. 195. 
a Nat. Hisk i. 279. 
