INDIRECT BENEFITS DERIVED FROM INSECTS. 221 



mighty mass, which seemed inferior in hardness only to iron, 

 is mouldered into dust, and its place occupied by younger 

 trees full of life and vigour. The insects to which this duty 

 is intrusted have been already mentioned in a former letter ; 

 but none of them do their business so expeditiously or ef- 

 fectually as the Termites, which ply themselves in such num- 

 bers and so unremittingly, that Mr. Smeathman assures us 

 they will in a few weeks destroy and carry away the trunks 

 of large trees, without leaving a particle behind ; and in 

 places where, two or three years before, there has been a 

 populous town, if the inhabitants, as is frequently the case, 

 have chosen to abandon it, there shall be a very thick wood, 

 and not the vestige of a post to be seen. 



I observed in a former letter, that the devastations of in- 

 sects are not the same in every season, their power of mis- 

 chief being evident only at certain times, when Providence, 

 by permitting an unusual increase of their numbers, gives 

 them a commission to lay waste any particular country or 

 district. The great agents in preventing this increase, and 

 keeping the noxious species within proper limits, are other 

 insects ; and to these I shall now call your attention. 



Numerous are the tribes upon which this important task 

 'devolves, and incalculable are the benefits which they are 

 the means of bestowing upon us ; for to them we are in- 

 debted, or rather to Providence who created them for this 

 purpose, that our crops and grain, our cattle, our fruit and 

 forest-trees, our pulse and flowers, and even the verdant 

 covering of the earth, are not totally destroyed. Of these 

 insects, so friendly to man, some exercise their destructive 

 agency solely while in the larva state ; others in the perfect 

 state only ; others in both these states ; and, lastly, others 

 again in all the three states of larva, pupa, and imago. For 

 order's sake, and to give you a more distinct view of the 

 subject, I shall say something on each separately. 



The first, those which are insectivorous only in their larva 

 state, may be further subdivided into parasites and imparasites, 

 meaning by the former term those that feed upon a living 

 insect, and only destroy it when they have attained their full 



