INDIRECT BENEFITS DERIVED FROM INSECTS. 149 



of a particular kind of crane-fly with pectinated antennae (Ctenophora J ), 

 and other insects, which there find an appropriate nutriment; and a 

 similar 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. Staphy- 

 linidce, Sphceridia, and other Coleoptera, are always found under heaps of 

 putrescent vegetables ; and an infinite number are to be met with in de- 

 composing 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 2 , 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 ab- 

 stract from them 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 larvie 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. 3 



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 

 transport 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 is 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 ! As soon as a tree is fallen, one tribe attacks its 

 bark 4 ", 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 fol- 

 lowed 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 



1 Curtis, Brit. Ent. t. 5. 



2 Surely Mr. Marsham's name for this gerus, Boletaria, is much more proper 

 than that, of Fabricius, Mycetophagus (Agaric-Eater), since these insects seldom eat 

 agarics. 



(Econ. Nat. Amcen. Ac. ii. 50. Stillingfleet's Tracts, 122. 



4 Maupertuis 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, that in that country 

 there are few or none of the bark-boring insects. 



L 3 



