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LETTER XXI. 



MEANS BY WHICH INSECTS DEFEND THEMSELVES. 



When a country is particularly open to attack, or surrounded by numerous 

 enemies, who fromcupidity or hostile feelings are disposed ta 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 resist^ 

 ance or escape, this innumerable race must soon be extirpated. That 

 such is the case, it shall be my endeavor 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 con- 

 sider 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. Tbe principal ^assiue means of defence with which insects are pro- 

 vided are derived from their color and form, by which they either deceive, 

 dazzle, 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 

 practiced eye which can distinguish them from it. Thus, one of our 

 scarcest British weevils (Cleonus nebulosus), by its gray color, spotted 

 with black, so closely imitates the soil, consisting of white sand mixed 

 with black earth, on which 1 have always found it, that its chance of 

 escape, even though it be hunted for by the lyncean eye of an entomolo- 

 gist, is not small. Another insect of the same tribe (Thylacites scabriculus), 

 of which I have observed several species of ground-beetles (Horpa- 

 lus, &,c.) make great havoc, abounds in pits of a loamy soil of the same 

 color precisely with itself; a circumstance that doubtless occasions many 

 to escape from their pitiless foes. Several other weevils, for instance 

 Chlorima nivca and cretacea, resemble chalk, and perhaps inhabit a chalky 

 or white soil. But the most surprising instance of this adaptation of the 

 color of an insect to that of the soil where it resides, is found in some of 

 the Mantis tribe separated 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 nymph state only, in the very midst of 



