SEASONAL HISTORY. 43 
adult. The plowing which the land receives at this time can hardly 
be called a plowing, but the ground is torn up to a depth of from 6 
to 12 inches. As the soil is dry, that disturbed is for the most part 
in large clods, so there is little chance that many pupae or adults 
will be disturbed. 
Those which by chance are disturbed are either killed outright or 
have to live under changed conditions until spring. If they happen 
to be pupse the chances must be very much against them, and they 
will probably either be injured by the sharp particles of dirt or will 
dry out. If the insects are in the adult stage they will have a better 
chance of survival, but here also they may be compacted into the 
soil and killed, or be eaten by birds, since, living under unnatural 
conditions, they are obliged to appear earlier in the spring than they 
would otherwise. Even when kept under laboratory conditions 
many of those disturbed in the fall can not live till the normal time 
of their appearance. 
Hibernation. 
The adults pass the severest part of the winter in the soil. If 
disturbed they winter in their pupal cells, where they are well pro- 
tected, as these are on the average about 6 inches below the surface. 
This tempers the winter for them very well, and moisture can reach 
them only after heavy rains, and these seldom if ever occur except 
at the latter part of the hibernating period. When the beetles are 
disturbed in the fall they dig down into the soil for shelter. The 
depth to which they go varies. In some cases, where the soil is 
powdery, they go down only about from 1| to 3 inches, but when 
the soil is partially made up of clods and full of cracks they are 
sometimes found from 4 to 6 inches below the surface. 
M0RTA1.ITY During Hibernation. 
Under ordinary circumstances and where the pupal cells are undis- 
turbed, a large percentage of the beetles emerge safely — at least this 
is so under laboratory conditions. One cage was watered and kept 
outdoors so that the beetles were subjected to conditions as severe 
as the ordinary field conditions, yet all came through safely. Of 
those disturbed in the fall, not enough have been tested to give 
representative figures, but thus far almost a third of those treated 
in this way have died during hibernation. 
Gradual Emergence from Hibernation. 
The time of the appearance of the beetles in the spring is influenced 
to a large extent by artificial agencies, the most important of which 
is spring plowing. This plowing, which takes place as soon as possible 
