TRACTS ON VARIOUS SUBJECTS, &c. 14T 



their appearance at a certain stage of the growth of the plants, 

 which seldom happens until they have been some time in blossom ; 

 and probably the generation of those insects, as supposed by Lord. 

 Bacon,* may take place at the time when a certain, yet invisible, 

 change has operated in the leaves of the haulm ; that is, when 

 they begin to have a tendency to putrefaction. This opinion 

 seems to be strengthened by recent observation ; for, accidentally, 

 I had a small patch of potatoes in the Plantation-house garden, 

 considerably more advanced in growth than a crop which closely 

 surrounded it; and I observed the haulm of this patch was swarm- 

 ing with caterpillars, and the whole was soon after destroyed, 

 whilst the adjoining younger plants were wholly untouched : nor 

 were these attacked until about a fortnight afterwards, when 

 they had arrived at a more advanced state of growth. 



It seems to me that the generation of the caterpillar may be 

 prevented by keeping the haulm in a young and tender state : 

 and this can readily be done by cutting it down after it has been 

 some time in blossom. If this cutting were to commence at about 

 9 or 10 weeks growth, f and to continue for a fortnight, the 

 potatoe farmer would secure about four or five tons per acre of 

 green fodder for his cattle, which would well repay any small 

 difference there might be in the produce of the potatoes. I have, 

 indeed, good reason to believe that this difference would be far 



* Lord Bacon observes, " the caterpillar is one of the most general of worms, and 

 lireedeth of dew and leaves : they breed in the spring chiefly, because then there is both 

 dew and leaf. And they breed commonly when the east winds have much blown ; the 

 cause whereof is, the dryness of that wind ; for to all vivification upon putrifaction, it is 

 requisite the matter be not too moist. Caterpillars, both the greatest and the most, breed 

 upon cabbages, which have a fat leaf, and apt to putrlfy." 



t A surer guide is to cut the haulm about ten days after it has blossomed : red blossoms 

 appear in 10 or 12 weeks ; and the white in 7 or 8 weeks after planting. 



