INDIRECT BENEFITS DERIVED FROM INSECTS. 261 



of orifices into the solid trunk are bored by others. The 

 rain thus insinuates itself into every part, and the action 

 of heat promotes the decomposition. Various fungi now 

 take possession and assist in the process, which is follow- 

 ed up by the incessant attacks of other insects, that feed 

 only upon wood in an incipient state of decay. And thus 

 in a few months a 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 al- 

 ready mentioned in a former letter (p. 235 — ) ; but none 

 of them do their business so expeditiously or effectually 

 as the Termites, which ply themselves in such numbers 

 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 

 insects are not the same in every season, their power of 

 mischief being evident only at certain times, when Provi- 

 dence, by permitting an unusual increase of their num- 

 bers, gives them a commission to lay waste any particu- 

 lar 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 



