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Ch. XLII.] 



AGENCY OF INSECTS. 



437 



Wilcke above mentioned 



Natur 



The Phalcena 



preserve the balance of power among species. 



stroUUla has the fir-cone assigned to it to deposit its eggs 



ume 



the cone and snperfluons seed; bnt, lest \the destruction 

 should be too general, the Ichneumon strohileUce lays its eggs in 

 the caterpillar, inserting its long tail in the openings of the 

 cone tiU it touches the included insect, for its body is too large 

 to enter. Thus it fixes its 

 which being hatched, destroys it.' * 



minute 



Entomologists enumerate many parallel cases where msects, 

 appropriated to certain plants, are kept down by other insects, 

 and these again by parasites expressly appointed to prey on 

 them.t Few, perhaps, are in the habit of duly appreciating 

 the extent to which insects are active in preserving the 

 balance of species among plants, and thus regulating in- 

 directly the relative numbers of many of the higher orders 

 of terrestrial animals. The peculiarity of their agency con- 

 sists in their power of suddenly multiplying their numbers to 

 a degree which could only be accomplished in a considerable 

 lapse of time in any of the larger animals, and then as 

 instantaneously relapsing, without the intervention of any 

 violent disturbing cause, into their former insignificance. 



It, for the sake of employing, on different but rare occasions, 

 a power of many hundred horses, we were under the necessity 

 of feeding all these animals at great cost in the intervals 

 when their services were not required, we should greatly 



t) 



which was capable at 



machine, such as the steam-ei 

 ly moment of exerting the same 

 it any consumption of food during 

 same kind of admiration is stroncrly 



periods of inaction. Th€ 

 excited when we contemplate the powers of insect life, in the 

 creation of which the Author of Nature has been so prodigal. 

 A scanty number of minute individuals, to be detected only 

 by careful research, are ready in a few days, weeks, or 

 months, to give birth to myriads, which may repress any 



^ Amccn. Acad. vol. vi. p. 26, § 14. 



t Kirby and Spence, vol. iv. p. 218 



»' 



