58 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
Soils 
Soils vary greatly in their water holding capacity, due for the most 
part to difference in physical make up. A sandy soil may have a maxi¬ 
mum water capacity of 11 or 12 % while in a silt loam soil, this may run 
as high as 40%. With deficient moisture, other conditions being equal, 
insect damage to crops will be the more severe on those soils having a 
low capacity to retain moisture. 
In that particular area in N orth Dakota where the pale western cut¬ 
worm has caused the most injury the soil is usually quite sandy. During 
periods of scant rainfall, this soil dries out quickly and there is little 
available moisture for plant growth. A mechanical analysis of the 
Beach fine sandy loam indicated 50% sands, 37% silt, and 11% clay. 
A soil of this character has a comparatively low capacity to hold moisture. 
There was much less injury on clay soils. An additional factor with the 
pale western cutworm is that the moths seem to prefer soil that is more 
or less loose in which to deposit their eggs. 
During the past two or three years, grasshopper damage has been 
conspicuous in certain counties in northern North Dakota. This 
region coincides almost exactly with the old bed of glacial Lake Souris, 
an area characterized in particular by soils with a high content of sands 
and therefore with a low capacity for holding water. Crops attacked 
by grasshoppers in this particular area have suffered severely mainly 
because the prevailing types of soil are those with a limited water holding 
capacity, which retards plant growth but does? not retard the insects 
attacking green plants. There is good reason to believe that the in¬ 
sects are no more abundant in this region than in other localities where 
less damage occurred. 
Conclusions 
In closing, it may be stated that the significance of much insect damage 
is not fully appreciated since it is often concealed. Much injury by 
insects is laid to other factors. Moreover, damage by insects may be 
influenced greatly by variations in temperature and moisture, both 
directly because of the effect on insects and also indirectly because of 
the effect on plant growth. Various types of soils in turn affect the 
severity of insect damage because of differences in the water holding 
capacity. 
By reason of these different factors, it is practically impossible to 
estimate, with any degree of accuracy, the relative importance of any one 
of them. Altho many factors are involved in the destruction of crops 
