520 THE STUDY OF INSECTS. 



There are certain other large, swiftly running ground- 

 beetles which resemble somewhat those just described. 

 These belong to the genus Cychrus (Cy'chrus), and may 

 be recognized by the long, narrow head, the wider or 

 more nearly circular wing-covers, and 

 by the fact that the wing-covers have 

 a very broad, reflected margin, which 

 covers a large part of the sides of the 

 thorax. 



The bombardier-beetles, Brachinus 

 (Bra-chi'nus). — There are many species 

 of beetles that have at the hind end of 

 Fig. 624. the body little sacs in which is secreted a 



bad-smelling fluid, which is used as a means of defence. 

 These beetles spurt this fluid out on to their enemies when 

 attacked. But in the case of the bombardier-beetles this 

 fluid changes to a gas, which looks like smoke as soon as 

 it comes in contact with the air, and is ejected with a sound 

 like that of a tiny pop-gun. When some larger insect tries 

 to capture one of these insect-soldiers, and gets very near it, 

 the latter fires its little gun into the face of its enemy. The 

 noise astonishes the pursuer, and the smoke blinds him. 

 By the time he has recovered from his amazement, the little 

 bombardier is at a safe distance. These beetles have quite 

 a store of ammunition ; for we have often had one pop at 

 us four or five times in succession, while we were taking it 

 prisoner. The bombardier-beetles belong to the genus 

 Brachinus, of which we have in this country about twenty- 

 five species. They are very similar in appearance ; the 

 head, prothorax, and legs are reddish yellow, 

 and the wing-covers are dark blue, blackish, or 

 greenish blue (Fig. 625). 



There is a common beetle that resembles 

 the bombardier-beetles quite closely in size and 

 color, but which may be distinguished by the 

 comb-like form of the tarsal claws ; this is Lebia grandis 



