INDIRECT BENEFITS DERIVED FROM INSECTS. 145 
makes it an object of cultivation, must expect that these agents will follow 
it into the artificial state in which he 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 vegetable 
productions, which were in danger of being destroyed by the exuberance of 
sone individual species, and thus are fulfilling the great law of the Cre- 
ator, 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 ma- 
terially injure our herbage, the wire-worm, the larvee of Melolontha vul- 
garis, Tipula oleracea, &c., 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 thongh 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 everywhere 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, preponderate over 
their evil ones. Mr, Clark is inclined to think that the gentle irritation 
of Gstrus Equi is advantageous to the stomach of the horse rather than 
the contrary. On the same principle it is not improbable that the Zabani 
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 
Slomoxys and other flies may prevent diseases that would be brought on 
by indolence and repletion And in the case of man himself, if Ido not go 
so far as Linné 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 which you 
will readily perceive have an intimate bearing upon it; and I shall, there- 
~ 1 Sparrman’s Voyage, i. 367. 
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