39 



A living wind-felled tree here was not attacked. Near No. 11 there are a num- 

 ber of peeled trees, two of which have a few Dendroctonus galleries at the base. 

 Several have Xyloterus and Tetropimn . but no evidence of attack has been noticed 

 above the peeled portion. The leaves on all of them are green, but some are begin- 

 ning to fade. A small log cut near by and left is full of Polygraphus, but contains 

 no Dendroctonus. No Dendroctonus were found here in stumps of last winter's 

 cutting. 



. Notes accompanying the report. 



The first activity of Dendroctonus was noted near Wight's on June 19, where a 

 tree girdled on June 13 had galleries in the bark as much as 14 inches long, with 

 eggs. Trees girdled on May 29 and others had galleries 2 inches long. At other 

 places I failed to note act vity of the insects on this date, except four or five bur- 

 rows in a stump, although I looked for it carefully n infested clumps of trees. 



The first larvae were noticed between July 28 and 31 at Big Island Pond. They 

 had then worked about an inch laterally from the parent galleries. 



On July 11 the trees at Wight's which were first infested had galleries as much 

 as 3 inches long, with eggs, but no larva?. On September 1 the same trees 

 showed the insect mainly in the pupa form; also so. i:e large larvae and recently 

 developed beetles. On October 4 the broods were largely in the full-colored or 

 matured adult form, though some lag ,ed behind, even remaining in the larval 

 form. At this date 1 could see no signs of any of the beetles emerging, although I 

 looked carefully. 



The trees girdled in June and July indicate the time required for the develop- 

 ment of the insect. The trees girdied on September 1, I believe, were in no case 

 attacked by insects. 



We had a very wet June, and early July was also wet, but the weather was dry 

 in late summer. On September 1 the leaves had not commenced to turn, but by 

 October 1 about half of the leaves of the maples had fallen, 



In my identification of the insects I was not always certain about. Tetropium 

 and Polygraphus. 



The woodpeckers that work on infested trees are probably American and 

 Arctic three-toed woodpeckers. There may be. others. They do little work in 

 the summer. 



It seems that any exposure of tie wood — as in girdling— attracts Xyloterus and 

 possibly Dendroctonus. 



Trees are frequently met with which are attacked quite abundantly by Den- 

 droctonus, which exc ivate galleries, but no broods develop. Such trees fre- 

 quently at least — I think generally — escape attack the next year. 



My inference as to the attraction exerted by g rdled trees is that while many 

 beetles are attracted to them, yet the attraction is not great or from a long dis- 

 tance. The evidence furnished by Group III is affirmative on this point. The 

 results with Group II are inconclusive, mainly from the abun .ance of the beetles 

 here, but also from exemption of tree No. 7. The results in the case of Group I 

 seem to show that distance is a bar, while those with Group II further indicate 

 that the broods migrate only a short distance. The evidence furnished by trees 

 Nos. 26, 27, and 28 in Group I is affirmative, but the surroundings are such that 

 the test is inconclusive. From Groups IV and V, I can draw no striking or certain 

 conclusions, while Group VI is the most affirmative of all. 



As to windfalls, I can only state from general impression that in my opinion 

 they are not specially liable to attack by Dendroctonus, and that the same is the 

 case with logs left in yards, tops left in woods, etc. 



The fact that 6 of the 9 trees girdled on June G were infested and killed, while 

 no others near by were attacked, is strong evidence that the girdled trees attracted 

 the insects. 



