36 SEVENTEENTH Report STATE ENTOMOLOGIST OF MINNESoTA—1918 
tions of men in the cedar yards who say that it is much less common 
to find ants in the heavy, sour butts from the swamps than in the light 
upland cedar. 
In every locality where studies were made, the percentage of trees 
infested averaged very nearly the same as that at Blackduck, which 
would make the average infestation for the state run between fifteen 
and twenty-five per cent in the swamps and from forty to seventy per 
cent on the higher land. Altho the factors resulting in the heaviest 
infestation occurring on the dry land just out of the swamp have not 
Fig. 8. Three trees left “hanging’’ because they showed ant injury on the butt. 
been determined, there are several possible theories. The first is 
that since the ants are land animals, they prefer the dry ground to 
the swamp, but this scarcely seems a satisfactory explanation since it 
would be perfectly possible for the ants to make their way about in 
the swamps without getting wet at practically any time of the year. 
It is possible, however, that the wet condition of the ground would 
tend to increase the moisture in the nests, making them less comfort- 
able and increasing the danger of an epidemic of s6me fungous parasite 
in the colony. 
The percentage of trees with heart rot is greater on the dry ground 
than inthe swamp. This factor may have considerable influence, since 
