59 



in contact with healthy caterpillars. The effect of this method 

 was observed in one case during the summer of 1910. In com- 

 pany with the division agent, Mr. Worthen, I came in touch 

 with a locality in Boxford where gypsy moth caterpillars were 

 gathered together in considerable numbers under tanglefoot 

 rings. It had been decided to kill the caterpillars with burning 

 oil, but I dissuaded the men from doing this by giving as my 

 opinion that the wilt would make its appearance in all prob- 

 ability in a few days. This assumption was right, for there 

 was seen, after three days, the first signs of the disease, which 

 then spread so quickly that in a few more days the caterpillars 

 had succumbed. 



Perhaps it might be worth while to work with the wilt in 

 different ways from those in the experiments described. There 

 is, for instance, the recapitulation of the experiments of 1909 on 

 a large scale. Caterpillars which had been killed by Flacherie 

 were mixed with water in different ways, and the mixture was 

 then either sprayed upon trees or was painted as rings around 

 the trunks. One or the other of these methods may prove to be 

 valuable, but the expense will be quite high, while the use of the 

 simple exposure method incurs but small expense. There might 

 be mentioned still another point; Dr. E. Fischer of Zurich, 

 the discoverer of the predisposition of caterpillars towards 

 Flacherie, wrote me some time ago the following directions for 

 developing Flacherie artificially in the field: cut some of the 

 larger roots of a tree that is infested with a sufficient number 

 of caterpillars, water frequently the ground around the cut 

 surfaces and put into the trunk as much water as possible 

 through a hole bored at an angle of about 45 to the base of 

 the tree. By these means the same unhealthy food is produced 

 on the tree as is otherwise obtained by the placing of twigs in 

 water. It is certain that the wilt can be developed artificially 

 in the manner just described, but such an experiment needs 

 constant attention, and trees thus treated are, of course, de- 

 stroyed. 



I doubt whether the gypsy moth will ever become extinct in 

 America, but the wilt will probably produce, first, a consider- 

 able reduction of the mass, and then it is to be hoped that the 



