184 INDIRECT BENEFITS DERIVED FROM INSECTS. 



diet is furnished to the grubs of the rose-beetle ( Cetonia aurata) by the dead 

 leaves and stalks usually to be found in the ant's nest. Staphylinida, 

 SphcBridia, and other Coleoptera, are always found under heaps of putrescent 

 vegetables ; and an infinite number are to be met with in decomposing fungi, 

 which seem to be a kind of substance intermediate between animal and 

 vegetable. The Boleti, in particular, have one genus of coleopterous 

 insects appropriated to them^, and the Lycoperdons another. — Stagnant 

 waters, which would otherwise exhale putrid miasmata, and be often the 

 cause of fatal disorders, are purified by the innumerable larvae of gnats, 

 Ephemera, and other insects which live in them and abstract from thern all 

 the unwholesome part of their contents. This, Linne says, will easily 

 appear if any one will make the experiment by filling two vessels with 

 putrid water, leaving the larvae in one and taking them out of the other ; 

 for then he will soon find the water that is full of larvae pure and without 

 any stench, while that which is deprived of them will continue stinking.^ 

 Benefits equally great are rendered by the wood-destroying insects. 

 We indeed, in this country, who find use for ten times more timber than 

 we produce, could dispense with their services ; but to estimate them at 

 their proper value, as affecting the great system of nature, we should trans- 

 port ourselves to tropical climes, or to those under the temperate zones, 

 where millions of acres are covered by one interminable forest. How is 

 it that these untrodden regions, where thousands of their giant inhabitants 

 fall victims to the slow ravages of time, or the more sudden operations of 

 lightning and hurricanes, should yet exhibit none of those scenes of ruin and 

 desolation that might have been expected, but are always found with the 

 verdant characters of youth and beauty ? It ig to the insect world that 

 this great charge of keeping the habitations of the Dryads in perpetual 

 freshness has been committed. A century would almost elapse before the 

 removal from the face of nature of the mighty ruins of one of the hard- 

 wooded tropical trees, by the mere influence of the elements. But how 

 speedy its decomposition when their operations are assisted by insects 1 

 As soon as a tree is fallen, one tribe attacks its bark^, which is often the 

 most indestructible part of it ; and thousands 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 followed 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 vigor. 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 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 



' Surely Mr. Marsham's name for this genus, Boletaria, is much more proper than that 

 of Fabricius. Mijcetophagus (Asraric-eater), since these insects seldom eat agarics. 



* OEron. Nat. Aman.''Ac. ii. 50. Slillingfleet's Tracts, 122. 



^ Manpertuis observes, that in Lapland he saw many birch trees lying on the ground, 

 which had probably been there for a very long time, with the bark entire, though the wood 

 was decayed. Hence we may probably infer, thai in that country there are few or none of 

 the bark-boring in.sects. 



