110 CANKER WORM. 



Mr. Tinker continues : "On account of the coldness of the weather 

 I have had to set a tin of tar mixture in a pail, and fill the space with 

 hot water, to make it fluid, so as to apply it with an old paint brush. 

 My man and I ran off one thousand trees this afternoon, in four hours 

 — second coat. The first coat takes longer. Amount of material used 

 for one thousand trees, averaging six inches in diameter, from three to 

 four gallons. The first coat takes about five gallons." 



In a former letter Mr. Tinker says : "Your letters of the 7th and 9th 

 are received, I got my tar on the 9th, and have been into the tar and 

 moths knee-deep since; have caught enough already to fence the farm, 

 but whether I shall succeed in catching the rest remains to be seen. I 

 have observed the same as you have: that they run at night, even with 

 the thermometer at eight degrees below freezing." I have not myself 

 had an opportunity to see them moving at so low a temperature, but 

 the above record shows that they will run on quite cold nights, provi- 

 ded it be not stormy. 



Later in the year, after the Canker-worm season was past, I wrote to 

 Mr. Tinker, inquiring the result of his experiments with tar. The fol- 

 lowing extract give the substance of his reply: "My etit'orts held the 

 Canker-worms somewhat in check, still they stripped a good many 

 trees ; but they left so early, and the trees growing fast, they have had 

 a good growth of wood since. But the tar must be put on every after- 

 noon, and the moths run this year nearly a month." He adds, sub- 

 stantially, that unless some plan can be invented that requires less 

 labor and looking after, he is satisfied that human eflbrt will not exter- 

 minate them. 



Other substances, which do not harden so rapidly, have been tried 

 as substitutes for tar. Some have used melted India rubber, and print- 

 ers' ink has been recently recommended in the "Boston Journal of 

 Chemistry." But tlie practical objection to all such applications is, 

 that they have to be kept fresh not only through the whole month of 

 lilarch and a part of April, but also in open weather, in the late fall 

 and winter. And Mr. Tinker's experience, like that of thousands who 

 have preceded him, shows that such remedies are at best but partial 

 and unsatisfactory. 



Ir. having been noticed that the Canker worm moths climb with dif- 

 ficulty over a hard smooth surface, attempts have been made to inter- 

 cept their progress by surrounding the trunks of the trees with strips 

 of glass and bands of polished tin. I have repeated these experiments 

 and find them, like many of the other methods that have been resor- 

 ted to, a partial but not complete preventive. If a moth be placed 



