———— 
se y°” ++ 2 
THE ROUGH-HEADED CORN STALK-BEETLE 7 
alent in days), provided that no months later than September are 
taken into consideration. 
From these results it would appear to be a fair inference that on 
the average each female, under conditions similar to those existing 
in the experimental cages, is capable of depositing an egg every day 
during the normal breeding season. if the season lasts between one 
and two months, a beetle during this period ordinarily may deposit 
from 30 to 60 eggs. 
GROW TH 
As previously stated, the egg after deposition enlarges until it is 
nearly or quite double its original size, and simultaneously changes 
its form until it is almost. globular (Pl. Il, 6-#). EHKggs measured 
at Charlottesville several days after deposition averaged about 2 
millimeters in length and 1.5 millimeters in diameter. Unfortu- 
nately no measurements of freshly laid eggs were made, but the 
weights of eggs in different stages of growth were determined with 
the following results: 
In one lot of 15 eggs, ali weighed within less than 48 hours after 
being deposited, a total weight of 0.02013 gram was obtained, an 
average of 0.001342 gram for each egg. Three days later this same 
lot weighed 0.04041 gram, an average of 0.002694 for each egg, 
practically twice the original weight. It was noted that one egg of 
this lot, on the second weighing, had not increased in size, possibly 
not having been fertilized, so that the average weight of an egg, 
at this time, was doubtless somewhat greater than the figures given 
indicate. 
In a second batch of 15 eggs, weighed when they were between 
10 and 11 days old, the total weight obtained was 0.05052 gram, 
an average of 0.003368 gram for each egg, or approximately 24 
times the average of an egg when deposited. 
In a third batch, consisting of 9 eggs estimated as 16 days old 
and nearly ready to hatch and 6 others which were at least 12 days 
old, the total weight obtained was 0.06538 gram, an average of 
0.004359 gram for each egg, or approximately 34 times the weight 
of a freshly deposited ege. 
No attempt was made to ascertain the cause of this increase in 
-size and weight of the ege by determining its dry weight, but it is 
doubtless due to the absorption of water by the egg from the sur- 
rounding soil. The fact that the dead egg referred to above had not 
perceptibly increased in bulk after remaining in the soil for three 
days indicates that only the living eggs are capable of absorbing 
water. 
MOISTURE REQUIREMENTS 
It appears evident, as intimated in the preceding section, that 
the presence of a certain amount of available moisture in the soil 
is an essential prerequisite for development. The point was tested 
experimentally at Charlottesville, and it was learned that the eggs 
perish if kept in dry soil. 
It is to be regretted that no quantitative determinations of the 
moisture requirements of the eggs were made, as these would have 
been of value in explaining the conditions under which the species 
