Observations on the Turnip Saw- Fly. 



381 



the plants were moist with dew, had no effect; quick-lime and 

 soot were tried with no better success, and scattering slaked lime 

 or coal-ashes over the plants is said to be useless ; as it is admitted 

 that in consequence of this application the larvae rolled off the 

 leaves, I do not concur in its inutility, and I think that it might 

 be attended even with good success, if it were done after rain or in 

 damp weather, for on being touched the larvae curl themselves up 

 and fall to the ground ; if therefore they were brushed off in the 

 evening, and the dusting of lime with wood or other ashes were 

 immediately to follow that operation, I doubt not but myriads 

 would perish, especially if the succeeding night proved cold and 

 frosty, as is not unfrequently the case in September, and I believe 

 even in August ; indeed, such is reported to have been the result. 

 As, however, it is stated that when shaken off, the active cater- 

 pillars will regain the leaves by day in five minutes, except under 

 circumstances already alluded to, it is evident that such appli- 

 cations must not be delayed, if any advantage is expected to be 

 derived from dusting or watering them upon the ground. 



A heavy roller passed over the field in the evening and at 

 night, is said to have destroyed the caterpillars whilst feeding, and 

 to have checked them, especially when repeated two or three 

 times, but it did not save the crop. It is only at an early stage of 

 the turnip's growth that rolling can be of service, for when 

 the plants have arrived at any size, as they generally have when 

 I have seen them thus attacked, they must be injured by such a 

 process^ and the roller itself cannot come in close contact with 

 the soil. 



Whilst any attempts are making to diminish or to extirpate the 

 caterpillars, the turnips should not be touched with the hoe ; few 

 of the larvae are killed by the operation, and, as their food is 

 thereby reduced possibly one-half, the remainder more speedily 

 and with greater certainty falls a sacrifice to their ravages ; more- 

 over hoeing by loosening and refreshing the earth renders it more 

 agreeable and better suited to receive the full-grown larvae, when 

 they are led by instinct to bury themselves ; but as soon as the 

 caterpillars have disappeared, the hoes may be set to work vvith great 

 advantage where the crop is only partially injured, for then it will 

 disturb and destroy multitudes of those that have entered the earth ; 

 and if this could be immediately followed by throwing salt and 

 water from a water-cart over the crop, it would have a most bene- 

 ficial influence, and this could be effected without much difficulty 

 or detriment where the turnips are drilled in, and the same liquid, 

 or even common water, if thus applied the instant the saw-flies 

 make their appearance, would drive them away also, as such a 

 state of the plants is not adapted to the deposition of the eggs ; and 

 the saw-flies themselves, although, from their polished surface, the 



