82 
The Bulletin 
MORTALITY OF THE PUPA 
INTot as extensive figures have been kept on the mortality of the pupa? 
as upon the mortality of the larvie. During 1915 147 pupae were 
observed; from this number 110 adults were secured, giving a total 
mortality of slightly more than 18 per cent. Whether this is com¬ 
parable to conditions as they exist in the field has not been determined. 
Observations made during the course of this project would lead one to 
believe, however, that this figure is somewhat high. The pupae used 
in this experiment rvere not often disturbed, and frequently the stalks 
of corn became moldy or decay set in before they were observed again. 
Usually the mold or bacteria present infected the pupae, causing their 
death in a majority of cases. 
This condition must be wanting or very unusual in the field, for 
out of hundreds of pupae observed in the field, both in cyperus and in 
corn, the writer has never seen a single decayed or moldy pupa. Hence 
it seems that we would be safe in concluding that a death rate of 18 
per cent is abnormally high for pupae. 
DURATION OF THE PUPAL STARE 
In 1911 fifty-three adults were reared from pupae whose larval stages 
had been followed. These all passed through the pupal stages in from 
eight to eleven days; the greater number maturing in nine days after 
they had pupated. 
In 1915 one hundred and ten adults were reared from pupae whose 
larval stages had been followed from the hatching of the egg. These 
matured in from four to twelve days; the greater number maturing in 
from seven to eight days. 
From these figures it would seem safe to conclude that seven to nine 
days represent the normal length of the pupal stage; the time, per¬ 
haps, inclining somewhat toward the longer time, as is represented in 
Fig. 58. 
As is mentioned elsewhere, variations in humidity seem to have very 
little effect upon the rapidity with which corn bill bugs pass through 
the pupal stage. The normal variations in temperature during the 
summer months seem to affect them only slightly, if at all, for the 
average time for pupae reared in an out-of-doors insectary during July 
is practically the same as for pupae reared in September. 
The length of time required for larval development seems likewise 
to have no influence upon the time required for pupal development. 
In other words, the average time required for a bill bug with a total 
larval period of twenty to thirty days to pass through the pupal stages 
is so near the same as the average time required for bill bugs that have 
a total larval period of thirty to forty days or forty to fifty days that 
we seem safe in concluding that the length of the larval period has 
no influence whatever upon the length of the pupal period (Fig. 59). 
