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LETTER XXI. 
MEANS BY WHICH INSECTS DEFEND THEMSELVES. 
Wuen a country is particularly open to attack, or surrounded by numerous 
enemies, who from cupidity or hostile 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 infinite 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 insignificant) 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 de- 
tail 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 instruments with 
which Providence has furnished it for this purpose. 
I. The principal passive means of defence with which insects are provided 
‘are derived from their colour and form, by which they either deceive, daz- 
zle, alarm, or annoy their enemies ; or from their substance, involuntary 
secretions, vitality, and numbers. 
They often deceive them. by imitating various substances. Sometimes 
they so exactly resemble the soil which they inhabit, that it must be a 
practised eye which can distinguish them from it. Thus, one of our 
scarcest British weevils (Cleonus nebulosus), by its gray colour, spotted 
with black, so closely imitates the soil, consisting of white sand mixed 
with black earth, on which I have always found it, that its chance of escape, 
even though it be hunted for by the lyncean eye of an entomologist, is not 
small. . Another insect of the same tribe (Thylacites scabriculus), of which 
Ihave observed several species of ground-beetles (Hanpalus, &c.) make 
_great havoc, abounds in pits of a loamy soil of the same colour precisely 
with itself; a circumstance that doubtless occasions many to escape from 
their pitiless foes. Several other weevils, for instance Chlorima nivea an 
-eretacea, resemble chalk, and perhaps inhabit a chalky or white soil, But 
-the most surprising instance of this adaptation of the colour of an insect to 
-that of the soil where it resides, is found in some of the Mantis tribe sepa~ 
wrated by M. Lefebvre under the generic name of Eremiaphila, of which he 
ihas given so interesting an account. These insects (which he met with in 
ithe nymph state only, in the very midst of the African desert, leading to 
the Oasis of Bahryah, about four days’ journey from the Nile, where he 
