No. 4.] SHADE-TREE INSECT PROBLEM. ill 



of trees that have been stripped for several years being 

 entirely destroyed or killed? 



Mr. Draper. We have had only a few. We have had 

 the beetle now six years. There are two trees which have 

 been stripped three years repeatedly, which are not entirely 

 dead, but the greater part of them is dead. 



Mr. Pratt. In case of the gypsy moth, two or three 

 strippings were death to the tree ; but I think the elm-tree 

 beetle does not work as severely on the tree as the gypsy 

 moth. 



Mr. Draper. I would like to say that I had a corre- 

 spondent in Paris who told me that three or four hundred 

 trees had died from repeated strippings, and that three or 

 four defoliations would kill them out entirely. But I think 

 the American elm would stand more. The English elm 

 might give it up after three or four years. 



Mr. Babb. One thing that remained with me from the 

 morning, brought out by Mr. Clark, was in regard to the 

 use of glucose with the arsenate of lead. The question 

 was not answered exactly this morning. I should like to 

 ask Mr. Kirkland about the use of glucose, — whether it 

 is necessary. 



Mr. Kibkland. In the early daj T s of the gypsy moth we 

 used glucose as a matter of course, and had faith in it ; but 

 there were some things that led us to doubt the advisability 

 of using it, and we made a series of experiments. We 

 sprayed some oak bushes with glucose and arsenate of lead, 

 and other bushes with the arsenate of lead in the same pro- 

 portion and no glucose. Professor Fernald with Mr. For- 

 bush saw those bushes a few weeks after. They could see 

 no evidence of difference in the two lots. We took the 

 foliage at the end of about six weeks, counted a number of 

 leaves from each bush, and fed them to caterpillars. The 

 killing of the caterpillars was practicallj r the same in each 

 case. In September, some months after the spraying, Ave 

 cut whole bushes and picked off the leaves from each lot, 

 and had an equal weight of those leaves examined by a 

 chemist, and he found practically no difference in the amount 

 of arsenic present. The next year we dropped the use of 



