38 



GENERAL ZOOLOGY 



their prey. Here, with the earth-colored head even with the 

 surface, they lie in wait, seizing any passing insect with 

 their strong jaws. 



Often there is found beneath stones in fields a small blue 

 oval insect, about two centimeters in length, which, when 

 handled, emits a puff of smoke-like gas with a strong odor, 



and a quite audible noise, as of 

 the report of a tiny pop-gun. 

 This is the bombardier-beetle 

 (Brack 1 inus). Its secretion be- 

 longs to the class of repellent 

 odors, and may often render possible the escape 

 of its possessor before the enemy has had 

 time to recover. The bombardier is one of 

 the large family of ground-beetles which are 

 found beneath sticks and stones everywhere. 

 Ground-beetles are generally black in color ; 

 most of them capture living prey. Some have 

 taken to cave life and have become blind. 

 In such cases hairs possessing the sense 

 of touch are well developed on the body, so 

 FIG. 20. Tiger-Bee- that the beetles run as swiftly as if they 

 tie and Larva, possessed eyes. 



Water-Beetles. The whirligig-beetles 

 (Dineu'tus, Fig. 21) are familiar, oval insects found in groups 



FIG. 21. Whirligig-Beetles. Natural size 



