16 NINETEENTH REPORT STATE ENTOMOLOGIST OF MINNESOTA—IQ22 
out in different parts of the Park in stands representing as wide a 
range of site conditions as could be found in the region under observa- 
tion. The plots were almost all two-tenths acre in area, but in a few 
cases it was found advisable to make them smaller, and then one-tenth 
acre was adopted as the unit area. 
Each tree in every plot was carefully examined for evidence of 
beetle attack. The litter was scraped away from the base of each tree, 
exposing the mineral soil, so that the location of all tunnels, both old 
and new, could easily be determined. Records for each plot were kept, 
showing in addition to the amount of infestation, the exposure, the 
size of trees, the condition of undergrowth, the number of trees per 
acre, and the presence of old or new cuttings near the plot. 
Considering Itasca Park as a whole, the infestation as indicated 
by these plots was much lighter than the data gathered in connection 
with the improvement cutting of 1920-22 would lead one to suppose. 
Of the 45 plots, 8 showed no sign of infestation. On more than 
two-thirds of the plots the infestation was Io per cent or less. On 
only four plots did the infestation exceed 25 per cent. On only one 
plot did every tree show signs of beetle work. In every instance where 
the infestation exceeded 25 per cent, freshly cut logs had been held 
over the summer season in the immediate vicinity of the plot. 
Table I. Percentage of Infestation in Standing Norway Pine 
Distance from logs 
Location a 
Less than 100 yds. 200 yds. 400 yds. 
OldMimnillecsite = verrnien o- 100 52 8 
Nicollet*cabin {7 5-cyei eens: 66 21 Gi 
SW% of SWY Sec. 3... 23 12 9 
The distribution of beetles as shown by sample plot studies proved 
without doubt that the infestation of green trees is correlated with the 
presence of green logs, fresh stumps, lightning-killed trees, or windfalls 
in the immediate vicinity. Apparently the beetles are also attracted 
to freshly burned areas, and as a result uninjured trees along the edge 
of a burn are likely to be more heavily infested than trees farther away. 
The abundance of infested trees immediately around the old mill 
site southeast of Mary Lake illustrates well the conditions usually 
found where freshly cut logs are piled near green trees during the 
growing season. On the plot nearest the mill 100 per cent of the 
trees showed evidence of beetle work. The amount of infestation 
diminished rapidly as the distance from the mill site increased. At 
