IXTRODUCTIOX. 9 



three feet in diameter, and a Imndred and fifty feet high? 

 In some places the whole woods, as far as you can see 

 around you, are dead, stripped of the bark, their wintry- 

 looking arms and hare trunks bleaching in the sun, and 

 tumbling in ruins before every blast."* The subterraneous 

 larva of some species of beetle has often caused a complete 

 failure of the seed-corn, as in the district of Halle in 

 1812. t The corn-weevil, which extracts the flour from 

 grain, leaving the husk behind, will destro}^ the contents 

 of the largest storehouses in a very short period. The 

 wire-worm and the turnip-fly are dreaded by every farmer. 

 The ravages of the locust are too well known not to be at 

 once recollected as an example of the formidable collective 

 power of the insect race. The white ants of tropical 

 countries sweep away whole villages with as much certainty 

 as a fire or an inundation ; and ships even have been 

 destroyed by these indefatigable republics. Our own 

 docks and embankments have been threatened by such 

 minute ravagers. 



The enormous injuries which insects cause to man may 

 thus be held as one reason for ceasing to consider the study 

 of them as an insignificant pursuit; for a knowledge of 

 their structure, their food, their enemies, and their general 

 habits, may lead, as it often has led, to the means of 

 guarding against their injuries. At the same time we 

 derive from them both direct and indirect benefits. The 

 honey of the bee, the dye of the cochineal, and the web of 

 the silk- worm, the advantages of which are obvious, may 

 well be balanced against the destructive propensities of 

 insects which are off'ensive to man. But a philosophical 

 study of natural history will teach us that the direct 

 benefits which insects confer upon us are even less import- 

 ant than their general uses in maintaining the economy of 

 the world. The mischiefs which residt to us from the 

 rapid increase and the activity of insects are merely results 

 of the very principle by which they confer upon us nrmi- 

 berless indirect advantages. Forests are swept away by 



* Amer. Oriiith., iii., p. 21. 



t Blumenbacli ; sec also Insect Transforniatious, p. 2ol. 



