404 



LETTER XXL 



MEANS BY WHICH INSECTS DEFEND THEMSELVES. 



WHEN 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 (Tl.ylacites scabriculus), of which 

 I have observed several species of ground-beetles (Harpalus, &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 and 

 cretacea, 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- 

 rated by M. Lefebvre under the generic name of Eremiaphila, of which he 

 has given so interesting an account. These insects (which he met with in 

 the njmph 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 



