302 TRANSFORMATIONS OF INSECTS. 
water; but there are other beetles which live in caverns, where 
no light ever penetrates, and they are consequently colourless, 
almost transparent, and blind; and there are also species which 
live in those parts of grottoes and caves where the gloom is less 
dense, and there is some light, and they have imperfect eyes. 
Blennis arecolatus—which was studied by Victor Audouin on the 
coasts of the island of Noirmontier—passes the greater part of its 
life at a very considerable depth below the surface of the water, 
and it is only found at low spring tides, when the sea has re- 
tired more than usual. It hides under stones, and in the crevices 
where a certain quantity of air is apt to remain; and it appears 
that the long hairs which cover the beetle keep a quantity of 
air-bubbles between them and the body, for the purposes of 
respiration. 
These beetles are mentioned with the hope that researches will 
be made at some time or other concerning their metamorphoses. + 
Another group is that of the Arachinide. They hide them- 
selves under stones and congregate together. They are well 
known on account of their peculiar manner of repulsing their 
enemies, for when they are disturbed they elevate their tails 
and eject a quantity of a vaporous fluid with a considerable noise. 
There are few things more curious than what happens when a 
sroup of these Bombardier beetles is disturbed by the stones 
which cover them being suddenly removed. Every beetle hastens 
to get out of the way, and begins by discharging its weapon, 
and as this goes on the smoky, cloud-like gas which follows the 
noise is sufficiently remarkable. The fluid which they eject is 
pungent, acrid, and volatile, so that it becomes a bluish vapour 
in contact with atmospheric air. Chemical tests prove that it is 
_a strong acid, and it is sufficiently acrid to produce the sensation 
of burning upon the skin. The apparatus and the secretion are of 
course superadded during metamorphosis to the usual structures 
of the larva. 
The Cicindelide, or the Tiger Beetle family, is not so nume- 
rous in its genera as that of the Carabide. They are very elegant 
beetles, and their tints are so varied that they are much sought 
after by naturalists. They have large jaws, long palpi, sharp 
and toothed mandibles, long and thin legs, so that like the family 
