110 
The Bulletin 
previously tried out very successfully in studying the diurnal activities. 
However, none of these beetles were ever seen after the last of August. 
Believing that the water-color paint used during 1912 might have been 
removed in the ordinary daily activities of the beetles, other pairs were 
marked by clipping their elytra during August, 1913 and 1914. Hone 
of these beetles were seen after mid-September and only a few after 
late August. Hot many were ever seen far from the place where they 
had been marked, although a few were recovered in adjacent fields. 
Hone of the beetles-marked in 1913 were recovered in 1914, and none 
of those marked in 1914 were seen in the spring of 1915. 
However, in spite of this negative evidence, the writer is of the 
opinion that the beetles leave the early corn-fields in late August, either 
traveling to late fields of corn or to patches of cyperus grasses. This 
conclusion is strengthened by the fact that the bill bugs seem to dis¬ 
appear from the corn-fields very suddenly, and there is some very strong 
evidence from observations made in the insectary to show that late in 
the season the adults seem to develop a sudden instinct to fly. This is 
perhaps true in the field, also, and would naturally account for the 
sudden disappearance of the beetles from the corn-fields, as in the 
insectarv all the beetles seem to acquire the instinct to fly at about the 
same time. 
We have made no direct observations in the field that the beetles fly, 
save the indirect deductions as outlined above. If the beetles do acquire 
the instinct to fly from the fields, it would aid very materially in dis¬ 
persing the species and would be a very important phase in their life 
cycle. 
Careful counts of the numbers of beetles per acre have been made on 
small plats averaging one-third acre each. In these counts an effort 
was made to secure every beetle present in the field. Some were un¬ 
doubtedly missed, but our counts usually showed an average of about 
1,100 beetles per acre in mid-August, this number dropping so suddenly 
that by the last week in August there would be on the average from 75 
to 100 beetles present per acre. 
MORTALITY DURING HIBERNATION 
The mortality during hibernation has varied greatly in our insectary 
experiments. It has ranged from about 10 per cent in some cages to 
over 90 per cent in other cages. Beetles for our hibernation experi¬ 
ments were placed in various kinds of cases. Some were placed in 
jelly glasses with varying amounts of sand and varying numbers of 
beetles in each glass. The mortality seemed to increase with the 
increased numbers of beetles in a single jelly glass. Some beetles have 
been held over winter in large screened cages, where they had on the 
average about six inches of soil in which to bury themselves. These 
cages were exposed out of doors, and the beetles usually went into the 
