PEOGEESS EEPOET ON THE EUROPEAN COEN BOEEE 
99 
lapse and break over in the field; (4) after infested plants with com- 
paratively small stems, such as oats and some of the weeds, are cut 
while in a green condition, with the consequent rapid withering or 
shriveling of the stems; (5) during the handling and shipment to 
market of infested plant products such as sweet corn ears or beets 
with tops; (6) from certain plant products, such as celery, after they 
are placed in underground pits; (7) from infested material which 
has been buried in the soil. This last is especially likely to occur 
where such material is buried or plowed under in the spring, or in 
the early fall to about November 1. Much of this migration is noc- 
turnal, an interesting habit which the species may have developed 
in an endeavor to escape natural enemies which are more active 
during the daylight hours. Observations conducted at night in 
Fig. 46. — Windfall Baldwin apple infested by migrating European corn-borer larvae. 
A common occurrence in areas of severe infestation. Medford, Mass., September 
15, 1922 
severely infested fields of corn have revealed great activity on the 
part of the larvae at this time. Where infested cornstalks or 
other plant remnants are cut and gathered in large piles during the 
fall and left in this condition in the field all winter, many of the 
contained larvae migrate to the outer and drier layers of the pile, 
or to adjoining shelter, in order to escape the excessive moisture 
prevailing in the interior of the pile. These outer layers usually are 
dry enough to be burned easily during late April or early May and 
thus destroy a large percentage of the borers contained therein. 
When the migrating larvae are only partially grown they may 
enter and feed upon any of the host plants of the species, providing 
such plants are in a green and succulent condition. When, however, 
the migrating larvae are fully grown and have ceased feeding, they 
may enter almost any plant material (fig. 46) which affords suitable 
shelter, or they may seek shelter in various locations, as will be 
subsequently shown. 
