TRACTS ON VARIOUS SUBJECTS, &c. 71 



" remains to be done, in order to perfect onr knowledije of the 

 " nature and modes of destroyinsj;- these very destructive insects." 

 — Farmer's Dictionary , see Grub. 



The preceding- detail undoubtedly affords a striking proof of a 

 clean fallow being one of the uiost etiectual modes of clearing 

 lands of the grub. It was, indeed, reasonable to suppose it would 

 be so ; because, if no vegetable substance remain in the soil, 

 for the sustenance of so voracious a creature— whether he be 

 newly hatched by the summer heats, or arrived at full growth, it 

 seemed, at least probable, tliat he must infallibly perish. Every 

 one can judge whether or not this fact has not now been clearly 

 established. 



In the first stage of these experiments I was, for a short time, 

 apprehensive that the plan recommended by the anonymous wri- 

 ter might not succeed ; because I observed that some of the 

 grubs, that were put up in paper, had discharged a considerable 

 quantity of earthy substance. It seems therefore probable, that 

 (like worms) the grubs, in some degree, subsist upon earth ; but 

 the results have shewn that they cannot possibly exist, even for a 

 few weeks, without vegetable food. 



A prolonged, or a repeated fallow would, no doubt, be more 

 efficacious than the short period of my experiments. This should 

 be given in warm and dry weather ; for it is then the eggs, depo- 

 sited by moths, bring forth the young grubs. — Upon these too, 

 in tlieir tender state, the effect would be more speedy than upon 

 grubs tliat are arrived at full growth. In this stage they are ex- 

 tremely tenacious of life. I have seen them survive, for half a 

 minute, upon ashes so hot that my fingers were burnt in a few 

 seconds. I have kept some i n a strong solution of tobacco — others 

 in a solution of alkali, and found them alive, after being twelve 

 hours in these steeps. The common roller has no effect upon 



