302 TRANSFORMATIONS OF INSECTS. 



water ; but there are other beetles which Hve 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. 

 Biennis arcolatus — 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 BracJiinidcB. 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 

 group 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 Cicmdelidcs, or the Tiger Beetle family, is not so nume- 

 rous in its genera as that of the CarabidcB. 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 



