26 THE CANADIAN ENTOMOLOGIST, 



of injured trees. Recently specimens were received from Dr. Fletcher 

 with the following statement in the letter accompanying them : 



" I now send you a few specimens and will ask you for a line or two 

 on them. It is named Xyleborus saxeseni by European specialists, and 

 is doing considerable harm to plum trees in England. Miss Ormerod 

 showed me the work and gave me the specimen. I told her ... I 

 would submit it to you. ... It was alive, with several others of 

 different ages, in a large flat cavity in a plum branch two inches in 

 diameter." 



The evidence I have been able to obtain from a somewhat extensive 

 study of the habits of this and other species of Xyleborus, leads me to 

 conclude that while they must have moist wood in which to develop a 

 brood and propagate the fungus upon which they feed, they all have a 

 decided preference for that of dead, dying, or at least unhealthy trees, be 

 they standing or felled, and in no instance have I found any species of the 

 genus entering the wood of any part of an uninjured and healthy living 

 tree. Even X. dispar, which has been recorded as infesting healthy wood 

 of fruit trees in Europe and this country, has not been observed by me 

 in healthy wood, although I have found examples of a species determined 

 by Eichhoff as X. dispar in the wood of a great variety of trees in West 

 Virginia'. X. xylograpJius comes nearer to attacking healthy wood of 

 living trees than any other species I have observed. It will attack living 

 trees, and has been frequently found in apparently healthy sapwood, but 

 in such instances it had entered through the dead or dying wood of a 

 wound or dead spot in the bark of the trunk or branches, as shown in 



Plate 3, fig. I. 



Even if it did attack perfectly healthy trees, it could scarcely be the 

 primary cause of their death, unless the insects should occur in such vast 

 numbers as to completely fill the sapwood with entrance galleries and 

 brood-chambers, which in large trees is hardly possible, and in small 

 trees not at all probable. In fact, they seem to prefer to excavate their 

 brood-chambers in the heartwood, which, as is well known, is not a vital 

 part of the plant structure. If the healthy living sapwood is penetrated at 



I. This statement is not meant to even suggest the inaccuracy of the records of 

 other writers, since I have reasons for doubting that the species I observed is a true X, 

 dispar^ and even if it is, habits of the same insect may difter under different environ- 

 ments. 



