222 [March, 



Mr. Ewart then proceeded to experiment as to whether any harm 

 was done by the larvse while in the " dip ;" but this, as was expected, 

 proved not to be the case. On the 3rd inst., he wrote : " Our experi- 

 ment showed that they do no harm while in the 'dip.' The injury is 

 only done when the cloth is in the heaps, so that we shall, I expect, be 

 able to steer clear of it in future." And in his last letter he says : 

 " It is a very, great matter that the cause of the damage has been 

 ascertained, and the means of avoiding it — which is, I believe, the case." 



The larvge which were found to gnaw the holes in the linen were 

 those of Agrotis exclamationis, and to this species I think it probable 

 that most of the damage may be attributed. They, as is well known, 

 hide during the day in the earth, or at the roots of plants, crawling 

 up at night to feed, but, probably, finding light and air excluded by 

 the linen, they crawl upon the under-side of it for the day, instead of 

 burrowing"underground, and thus get gathered up with it. Then at 

 night, being hungry, and finding themselves confined in the heap of 

 linen, and under pressure, they act just as they would when under- 

 ground, if necessary — use their strong jaws, and their hard heads, and 

 dorsal plates to force their way through the opposing substance. 



I think that Mr. Ewart, by the patience and acuteness with which 

 he has tested their proceedings, step by step, has completely cleared 

 up the difficulty, and found a preventive to the mischief. Even if 

 the linen cannot be put into the " dip " directly it is raised from the 

 grass, all injury can be prevented by the simple process of shaking 

 every larva off it before laying it in the heaps or on the racks. But, 

 probably, the workpeople could hardly be relied upon always to do 

 this, and Mr. Ewart's plan is doubtless the best. At any rate, the 

 discovery that the damage is not done while the linen is on the grass, 

 and so accessible to the larvce, sweeps away all the difficulty. 



I am much gratified at the result of these experiments. Irish 

 industries are not numerous, and the removal of a serious source of 

 damage to one of the most important of them will, I hope, be of 

 great advantage. Linen is cut off for sale wholesale in lengths of 60 

 yards, and holes through which a half-grown Noctua larva can crawl 

 would very seriously affect their value, if not render them unsaleable. 



It is curious to find that the Agrotis larva? are not injured in any 

 way by long immersion in a weak solution of chloride of lime ! Had 

 the immersion been simply in water, it would have been no more than 

 ground-feeding larva) must often expect at this season of the year. 



King's Lynn, Norfolk : 



December 10th, 1888. 



