202 On the Insects affecting the Turnip Crop. 



from the insect ; and that when the growth is slowest^ the danger 

 from the insect is most serious." This arises in a great measure 

 from the advantage that insects have over vegetation ; a gleam of 

 sunshine is ahnost sufficient to call them into active life^ as we 

 have before observed^, and as is evident from the swarms of deli- 

 cate gnats that may often be seen dancing in the air when frost is 

 on the ground even in January ; but it requires the accumulated 

 rays of the sun, and a much longer duration of warmth, to set in 

 action the fluids of plants. 



It will not be irrelevant to the subject to take a cursory view of 

 the recommendations suggested by various eminent agriculturists ; 

 and as the results derived from some of their experiments have 

 been greatly at variance, I may venture occasionally to offer an 

 opinion ; but as it is not strictly within my province to determine 

 such practical points of difference, I can only hope that they may 

 be encouraged to prosecute their valuable researches until such 

 variations are satisfactorily explained. 



Whether any direct protection against the beetle can be ex- 

 pected from manure, since it is ascertained that it is not upon the 

 seeds that the eggs are laid, now becomes a question ; for when 

 the maggots escape from their burrows in the leaves, and enter 

 the earth, in order to become chrysalides, before changing to 

 beetles, the manure, I should think, seldom contains sufficient 

 ammonia to destroy them, and, if I mistake not, any moderate 

 fermentation would rather facilitate than retard their metamor- 

 phoses; moreover, the instinct of insects is so perfect, that the 

 maggot would most assuredly avoid obnoxious spots, so that, if 

 any manure were spread that would injure them, unless it formed 

 a very uniform stratum, it would not insure success, although 

 great advantages might be derived from its use. 



Burning has been found the best preventive against the beetle 

 by some, which is readily accounted for, since it would destroy 

 any chrysalides in the land, and as the beetles may be in abund- 

 ance in the field when it is preparing for turnips, burning v/ould, 

 of course, be destruction to them, and spreading the ashes after- 

 wards over the ground will prove an additional security ; but such 

 a system does not suit sandy soils, neither can it be followed up 

 regularly on any land. . 



Feeding off" the turnips is strongly recommended as an antidote 

 to the beetle, as well as from its peculiar advantages of manuring 

 and preparing the land for the barley-crop and succeeding seeds. 

 I am disposed to attribute the advantages derived from sheep- 

 folding, as regards the beetle, to the perfect stamping down of 

 the soil and herbage, by which all insect life is destroyed, rather 

 than to any peculiar quality in sheep -manure, unless it be con- 

 tained in their urine. 



