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 veiy 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. c 24 . 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 
