24 COMMON BRITISH INSECTS. 



Gravesend, and ten or twelve may sometimes be seen 

 under a single stone, firing off their artillery when 

 deprived of their shelter. 



The volatile fluid which produces such curious 

 effects is secreted in a little sac just within the end of 

 the abdomen. It is not only capable of repelling the 

 larger Beetles by its explosion and cloud of blue 

 vapour, but is potent enough to discolour the human 

 skin when discharged against it, as many have found 

 who have captured Bombardier Beetles by hand. 

 Should it get within the eyelids, the pain and irrita- 

 tion produced resemble those which would be caused 

 by a corresponding amount of the strongest vinegar. 



The whole of the contents are not ejected at one 

 discharge, but there is sufficient to produce a series of 

 explosions, each perceptibly fainter than its prede- 

 cessor. Even after the death of the Beetle, the 

 explosions may be produced by pressing the abdomen 

 between the finger and thumb. Even in our small 

 British species the phenomenon is very surprising, 

 but there are much larger species in hotter countries, 

 which produce much louder explosions, accompanied 

 with quite a cloud of vapour. Three British species 

 of Brachinus are known to entomologists, the remain- 

 ing two, however, being extremely rare. 



WE come now to another family of Geodephaga, 

 of which we can but take one example. The 

 Scaritidae, like the preceding family, are seldom seen 

 in the open air, but, instead of creeping into clefts 

 already existing, they make tunnels for themselves. 

 Tunnelling Beetles are almost invariably cylindric 



