18 NINETEENTH REPORT STATE ENTOMOLOGIST OF MINNESOTA—IQ22 
forest was undisturbed by cutting, windfall, lightning, or fire, beetle 
infestation was seldom found. Without exception all of the nine 
uninfested plots were so located. 
3efore this study was undertaken, it was suspected that site con- 
ditions, density and composition of stand, age and size of trees, density 
of underbrush, and other such factors might have some influence in 
determining the extent of beetle infestation, but no such relation ts 
apparent. The examination of the sample plots, however, does demon- 
strate conclusively a specific relationship between infestation of stand- 
ing trees by the red turpentine beetle and the presence in the immediate 
vicinity of green logs, fresh stumps, windfalls, or injured trees. 
Doubtless the beetles are attracted by this freshly cut or iniured 
material. 
Naturally, where so many trees were infested, as indicated by the 
data gathered on the sample plots, one might expect a considerable 
number of trees to succumb to the beetle attack. Such an assumption, 
however, did not prove to be true. Strange to say, not a single tree 
was killed by the beetles on any of the plots examined. In one case a 
tree was attacked so heavily that its death was probably only a ques- 
tion of time, but it was still alive when examined. ‘The only tree 
observed that was without doubt killed by this beetle was a large 
Norway pine, standing alone near the mill site referred to above. This 
tree had been attacked at fifty-three separate spots about the base. Brood 
had been reared in only three of these tunnels. Another large tree 
near was spotted about the base with forty-five pitch tubes. No brood 
had been reared in any of the tunnels, and the tree was apparently 
perfectly healthy and growing normally. 
It was exceedingly rare to find any brood emerging from infested 
living trees. Usually the adult beetles tunnelled into the tree and, after 
a longer or shorter battle with the flow of resin, they were either over- 
whelmed and drowned or were forced to leave. From this it would 
appear that the beetles attacking living trees are either misguided 
individuals whose instinct leads them to impossible breeding grounds, 
or they are the overflow which can not be accommodated in the avail- 
able material suitable for breeding. 
In this connection it must be remembered that all the dead trees 
on much of the area studied were taken out in the course of the im- 
provement cutting mentioned. Much of the evidence of past beetle 
work had been removed before this study was undertaken. Therefore 
this report describes conditions only as they exist at present! “tas 
certain that with the passing of logging operations in and about the 
