92 BULLETIX 1476, U. S. DEPARTMENT OF AGRICULTURE 
EFFECT OF COVERING EGGS WITH SOIL 
During the operation of cultivating small corn plants, some of the 
lower leaf blades bearing egg clusters often are covered lightly with 
soil. This treatment does not prevent the eggs from hatching, and, 
unless covered to a depth of at least 4 inches, most of the newly 
hatched larvae are able to make their way to the surface of the 
soil. In June and July, 1920, a total of 56 clusters of fertile eggs of 
the first generation were buried in damp sand-loam soil at depths 
varying from 1 to 4 inches. All of these eggs hatched. At a depth 
of 1 inch all of the resulting larvae came to the surface of the soil, 
at 2 inches 57 per cent, at 3 inches 57 per cent, while at a depth of 
4 inches none of the larvae were able to reach the surface of the soil. 
EFFECT OF TOTAL IMMERSION IN WATER ON HATCHING 
During August, 1920. experiments were conducted to determine the 
effect of total immersion in fresh water upon the hatching of the 
eggs. The results of these experiments showed that fertile eggs did 
not hatch after a period exceeding 6.5 hours of total immersion. 
This fact may be of importance when treating plants or plant 
products bearing P. nubilalis egg clusters. 
FEEDING HABITS OF LARVAE 
The general feeding habits of P. nubilalis larvae have been pre- 
viously discussed with relation to the character of injury to corn and 
to other plants. 
METHOD OF FEEDING 
The method of feeding by P. nubilalh larvae, as distinguished from 
their boring habits, is subject to a wide variation in accordance with 
the habits of individual larvae and with the stage of development of 
the plant, as well as with the part of the plant attacked. 
When the eggs are deposited upon young corn plants of which the 
tassel has not yet appeared, the newly hatched larvae feed at first 
upon the upper and lower surfaces of the tender leaf blades, thus 
excavating small irregular-shaped areas in the epidermis. Some 
of the small larvae may also perforate the leaf blades surrounding 
the tassel, or work their way between the leaf blades and feed upon 
the developing tassel within. Once inside the tassel cavity, they 
feed upon and within the tassel buds. As the tassel expands and 
the larvae become larger, they enter the tassel stem or its branches 
and feed within. Instead of feeding upon and within the tender 
leaf blades and tassel, some of the newly hatched larvae habitually 
migrate to points lower down on the same or near-by plants, where 
they may enter the plant at practically any point, although their 
favorite place of entrance is between the leaf sheath and the stalk. 
Later in the development of the plant many of the larvae also enter 
between the stalk and the base of the ear, or they may enter the ear 
directly. 
When the eggs are deposited upon corn plants which have reached 
the tassel stage, the newly hatched larvae usually do not attack the 
tassel, nor do they feed to any extent upon the surface of the leaf 
blades; under these circumstances they enter the stalk directly, or 
the thick midrib of the more tender leaf blades. If the plant has 
developed an ear, the newly hatched larvae frequently feed upon the 
