'250 INDIRECT BENEFITS DERIVED FROM INSECTS. 



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 pas- 

 tures, 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 

 CEstms Equi is advantageous to the stomach of the horse 

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

 improbable that the Tabani often act as useful phleboto- 

 mists 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 w^ould 

 be brought on by indolence and repletion. And in the 

 case of man himself, if I do not go so far as with 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 which you will readily perceive 

 have an intimate bearing upon it ; and I shall therefore 

 proceed to point out the more evident benefits which we 

 derive from insects, arranging them under the two great 

 heads of direct benefits, and those which are indirect } 

 beginning with the latter. 



