LETTER XXI. 
MEANS BY WHICH INSECTS DEFEND 
THEMSELVES. 
WHENa country is particularly open to attack, or sur- 
rounded by numerous enemies, who from cupidity or hos- 
tile feelings are disposed to annoy it, we are usually led to 
inquire what are its means of defence ? whether natural, or 
arising from the number, courage, or skill of its inhabitants. 
The insect tribes constitute such a nation: with them in- 
finite hosts of enemies wage continual war, many of whom 
derive the whole of their subsistence from them: and 
amongst their own tribes there are numerous civil broils, 
the strong often preying upon the weak, and the cunning 
upon the simple: so that unless a watchful Providence 
(which cares for all its creatures, even the most insignifi- 
cant,) had supplied them with some mode of resistance or 
escape, this innumerable race must soon be extirpated. 
That such is the case, it shall be my endeavour in this 
letter to prove; in which I shall detail to you some of the 
most remarkable means of defence with which they are 
provided. For the sake of distinctness I shall consider 
these under two separate heads, into which indeed they 
naturally divide themselves :—Passive means of defence, 
such as are independent of any efforts of the insect ; and 
active means of defence, such as result from certain efforts 
of the insect in the employment of those instincts and 
