180 INDIRECT BENEFITS DERIVED FROM INSECTS. 



it into the artificial state in which lie has placed it, and still prey upon it ; 

 and it is his business to exert his faculties in inventing means to guard 

 against their attacks. It is a wise provision that there should exist a race 

 of beings empowered to remove all her superfluous productions from the 

 face of nature ; and in effecting this, whatever individual injury may arise, 

 insects must be deemed general benefactors. Even the locusts which 

 lay waste whole countries clear the way for the renovation of their vege- 

 table productions, which were in danger of being destroyed by the exube- 

 rance of some individual species, and thus are fulfilling the great law of the 

 Creator, that of all which he has made nothing should be lost. A region, 

 Sparrman tells us, which had been choked up by shrubs, perennial plants, 

 and hard half-withered and unpalatable grasses, after being made bare 

 by these scourges, soon appears in a far more beautiful dress, clothed with 

 new herbs, superb lilies, and fresh annual grasses, and young and juicy 

 shoots of the perennial kinds, affording delicious herbage for the wild cattle, 

 and game.^ And though the interest of individual man is often sacrificed 

 to the general good, in many cases the insect pests which he most 

 execrates will be found to be positively beneficial to him, unless when 

 suffered to increase beyond their due bounds. Thus the insects that 

 attack the roots of the grasses, and, as has been before observed, so 

 materially injure our herbage, the wire-worm, the larvae of Melolontha 

 vulgaris, Tipula oleracea, &ic., in ordinary seasons only devour so much 

 as is necessary to make room for fresh shoots, and the production of new 

 herbage ; in this manner maintaining a constant succession of young 

 plants, and causing an annual though partial renovation of our meadows 

 and pastures. In the rich fields near Rye in Sussex I particularly 

 observed this effect ; and I have since at home remarked, that at certain 

 times of the year dead plants may be every where observed, pulled up 

 by the cattle as they feed, whose place is supplied by new offsets. So 

 that, when in moderate numbers, these insects do no more harm to the 

 grass than would the sharp-toothed harrows which it has been sometimes 

 advised to apply to hide-bound pastures, and the beneficial operation of 

 which in loosening the sub-soil these insect borers closely imitate. 



Nor would it be difficult to show that the ordinary good effects of 

 some of those insects, which torment ourselves and our cattle, prepon- 

 derate over their evil ones. Mr. Clark is inclined to think that the gentle 

 irritation of (Estrus Equi is advantageous to the stomach of the horse 

 rather than the contrary. On the same principle it is not improbable that 

 the Tahani often act as useful phlebotomists to our full-fed animals ; 

 and that the constant motion in which they are kept in summer by the 

 attacks of the Stomoxys and other flies may prevent diseases that would 

 be brought on by indolence and repletion. And in the case of man 

 himself, if I do not go so far as Linne to give the louse the credit of 

 preserving full-fed boys from coughs, epilepsy, &-c., we may safely regard 

 as no small good the stimulus which these, and others of the insect 

 assailants of the persons of the dirty and the vicious, afford to personal 

 cleanliness and purity. 



I might enlarge greatly upon the foregoing view of the subject, but 

 this is unnecessary, as numerous facts will occur in subsequent letters 



* Sparrman's Voyage, i. 367. 



