150 BULLETIN 1476, U. S. DEPARTMENT OF AGRICULTURE 
single-generation seasonal cycle at the close of 1926. Two-generation 
material treated in a similar manner retained the seasonal cycle of its 
original habitat in the same series of experiments. Since these ex- 
periments were conducted in the United States, where the corn borer 
may not yet have become thoroughly adapted to its environment, the 
results thus far obtained must be accepted with caution. All experi- 
mental cross breeding of two-generation and one-generation individ- 
uals has resulted in the production of two-generation progeny. 
It has been demonstrated that the seasonal history, and especially 
the number of generations annually, is greatly influenced by the sea- 
sonal distribution of temperature and precipitation. 
LARVAL HABITS 
Studies to determine the percentage of larval establishment on corn 
have shown that an average of from 10 to 15 per cent of all larvae 
emerging from the eggs succeed in establishing themselves in or on 
the plant and reach maturity. This percentage of larval establish- 
ment may vary greatly in individual instances according to climatic 
conditions, type, variety, and strain of corn, and the condition of 
the individual host plant. 
Definite records were obtained, as a result of extensive studies, 
that less than 1 per cent of full-grown larvae were able to migrate 
for a distance of 30 feet. About 2 per cent of the borers involved 
migrated a distance of 25 feet. The typical farm fence row, or field 
border, provides an ideal shelter for larvae migrating from plowed 
fields or elsewhere, particularly when such refuges contain large 
growths of weeds. 
The average winter mortality above ground remains at about 10 
per cent, as previously reported, and there does not appear to be 
any climatic limitation to the distribution or multiplication of the 
borer which depends upon winter mortality. Moisture secured by 
contact immediately prior to pupation seems essential for over- 
wintering larvae. 
Although many of the larvae contained in cornstalks that were 
stored indoors died as a result of the deprivation of contact moisture 
(so essential for the completion of histolysis) and the subsequent 
development of the survivors was dela} T ed, a very large percentage 
of such larvae completed their development under storage condi- 
tions similar to those found on the average farm. Moreover, adults 
emerging from such storage conditions late in the season deposited 
eggs which developed into mature larvae before the end of the season. 
ADULT HABITS 
Detailed biological studies have demonstrated that the fecundity 
of the moths is greatly influenced by the character of the weather 
which occurs during their period of oviposition. Warm nights with 
abundant moisture, and the absence of heavy dashing rains, are 
conducive to maximum oviposition. 
A study of wind movement during the flight period of European 
corn borer adults, in the Lake Erie region, has indicated strongly that 
dispersion to neighboring States probably occurred from the severely 
infested areas of Ontario. This method of natural dispersion was 
