185 



DR. HOPKINS: That is not known. We have no way of 

 determining how far they will go. But they have wings and can 

 fly. There is no reason why they should not go long distances, 



DE. REED, of Virginia: I would like to ask how many of 

 these insects are borers in the chestnut that would inflict any 

 wound in the bark which would be large enough to allow infec- 

 tion by a fungus? 



DR. HOPKINS: There are a number of insects which may 

 cause wounds which will give entrance to the spores. When the 

 insects hatch from the eggs, they are almost microscopic ; there- 

 fore, the burrows made going into the bark will hardly give en- 

 trance to the spores unless there is a flow of sap from these small 

 wounds, which sometimes happens. My observation in Virginia 

 and the section south of Washington indicates that there is a 

 disease, possibly a bacterial one, which does get into these minute 

 wounds, on account of a small amount of the sap oozing out, 

 and in that way it works into the cambium. This is only a pos- 

 sibility which lias been suggested time and time again to me by 

 my observations ; perhaps it acounts for the fact that great num- 

 bers of dead trees in the South, do not show any traces of insects. 

 The trees die and the bark falls off and yet they show no evi- 

 dence of insects. Of course, the majority of dead trees do show 

 such evidence. We have had a man down in North Carolina in 

 1903-1904 studying the insects, and trying to determine the cause 

 of the extensive death of the timber in that state, and there was 

 no doubt that a great many of the trees were killed by insects, 

 but that insects were not the cause of all of the trouble. 



DR. REED : Is there any part of the tree which is invariably 

 attacked by these insects, or does it occur generally on the 

 tree? 



DR. HOPKINS : The principal point of attack, the most vital 

 part of a tree, is the middle trunk. We have found, in the study 

 of insects which kill trees, that they attack the middle portion 

 of the trunk. They girdle the tree at that point. The two- 

 lined chestnut borer does this especially. Other insects attack 

 all parts of the tree including the leaves, and some of them are 

 associated with the chestnut blight, as has been determined by 

 Mr. Craighead, who has been carrying on work under my instruc- 

 tion here in Pennsylvania. 



