April, ’20] McCOLLOCH: OVIPOSITION OF THE CORN EARWORM 255 
the daily number of eggs deposited on 128 individual plants and the 
silking period of 128 rows of corn. 
Three distinct broods of the corn earworm occur each year, the first 
brood of moths emerging early in June, the second brood about July 
10, and the third brood about August 10. The maximum emergence 
occurs about two weeks after the first emergence. The first two broods 
are of little importance in comparison with the third brood. 
The date of silking is dependent on the variety rather than on the 
date of planting. While the plantings were made at intervals of two 
weeks, the dates of silking show a difference of less than a week for 
corn planted April 15, May 1, and May 15. 
The moths show a decided preference for the silks for oviposition. 
When these are not available, the upper surface of the leaves and the 
stalks are selected. Relatively few eggs are deposited on the lower 
surface of the leaves, the husk, or the tassel. 
There is a distinct relation between the date of planting and the 
number and location of the eggs. From the data presented, April 15 
is too early to plant corn from the standpoint of oviposition, and June 
1 is too late. The variety of corn, however, is to be considered in 
developing the optimum date to plant corn, since each variety exhibits 
certain variations which will have an influence on the number of eggs 
deposited on it. An analysis of the data indicates that from the stand¬ 
point of the number of eggs deposited, Boone County White can be 
planted from April 15 to May 1; Commercial White about May 1; 
and Kansas Sunflower and Hildreth from May 1 to May 15. Consider¬ 
ing the results for the four varieties, May 1, under favorable conditions, 
is the optimum time to plant corn to escape the corn earworm. 
Considerable variation has been noted in the number of eggs de¬ 
posited on the four varieties of corn. In 43.7 per cent of the plots 
grown in the six years, Boone County White has had the lowest number 
of eggs. Kansas Sunflower has had the fewest eggs in 28.3 per cent 
of the plots, Commercial White in 15.6 per cent, and Hildreth in 12.5 
per cent. A similar variation was noted in the location of the eggs on 
the different varieties. There are a number of factors to be considered 
with relation to oviposition on varieties of corn, the principal ones 
being the time and period of silking, the time of maturing, and certain 
morphological characters of the plant. 
President W. C. O’Kane: The next paper is by R. W. Leiby. 
THE CORN-STALK BORER, DIATRAEA ZEACOLELLA DYAR 
By R. W. Leiby, Raleigh , N . C . 
(Withdrawn for publication elsewhere) 
7 
