PROGRESS REPORT ON THE EUROPEAN CORN BORER 
91 
hatching. At this time the developing larva is curled up inside the 
egg with its mandibles resting upon the next to the last abdominal 
segment. These mandibles soon begin to move laterally, and the 
larva straightens itself out in such a manner that the mandibles are 
brought into contact with the eggshell. A slit in this is soon made 
and the larva crawls forth. After hatching, the larva feeds to some 
extent upon the empty eggshell, but has not been observed to entirely 
devour it. 
FERTILITY AND HATCHING 
The greater proportion of eggs deposited in the field and in the 
insectary were found to be fertile. Table 28 gives data relating to 
the percentages of fertile eggs, as observed during the progress of 
life-history studies at Arlington, Mass. The percentages of fertile 
eggs which hatched, excluding parasitism, are also shown. 
Table 28. — Fertility and hatching of Pyrausta nubilalis eggs (New England) 
In insectary 
In field 
Generation 
Eggs un- 
der ob- 
servation 
Fertile 
eggs 
Fertile 
eggs 
hatching 
Eggs un- 
der ob- 
servation 
Fertile 
eggs 
Fertile 
eggs 
hatching 
First, 1919 
Number 
13, 893 
27, 285 
14, 886 
19, 646 
4,053 
20, 727 
Per cent 
87.2 
94.3 
89 5 
85.7 
96.1 
97.2 
Per cent 
Number 
Per cent 
Per cent 
Second, 1919 
2,245 
98.1 
98.9 
First, 1920 
95.7 
96.4 
Second, 1920 . 
First, 1921 
Second, 1921 
Second, 1923 . 
5,232 
94.3 
Average ._ ... 
91.5 
96.0 
95.4 
98.9 
From Table 28 it may be noted that an average of 91.5 per cent 
of the eggs deposited in the insectary were fertile, and 95.4 per 
cent of the eggs observed in the field were fertile. An average of 
96 per cent of the fertile eggs deposited in the insectary hatched, 
and 98.9 per cent of those hatched upon which observations were 
made in the field. 
An average of 97.2 per cent of the eggs hatched under insectary 
conditions at Sandusky, Ohio, during 1923 and 1924. A total of 
22,494 eggs were under observation in these experiments. At Silver 
Creek, N. Y., an average of 73.6 per cent of the eggs hatched under 
insectary conditions during this same period. A total of 25,690 
eggs were under observation in this series. In a total of 11,320 eggs 
collected in the field in Ohio during 1924 an average of 99.3 per cent 
were fertile. 
EFFECT OF DIRECT SUNLIGHT ON HATCHING 
Direct sunlight appears to prevent the hatching of the eggs of 
P. nubilalis. During July, 1920, several leaves bearing clusters of 
fertile eggs were removed from life-history cages and inverted in 
such a manner as to expose the eggs to direct sunlight. Under these 
conditions none hatched. In the field the eggs usually are deposited 
upon the undersides of the leaves and are not directly exposed to 
the sun, although they have been found infrequently on the upper 
sides of the leaves and upon the stems of plants, as well as upon the 
husks of ears of corn. 
