October, ’24] barber: European corn borer migration 583 
previous time in the history of this insect in the United States. In some 
fields the infestation was at the rate of from one and a half to two 
millions of borers per acre of sweet corn. Such great abundance of 
the insect caused, in some instances, an overpopulation of borers or, 
there were present in some fields a larger number of larvae than there 
was food present to satisfy. 
Migrating larvae were then very numerous and during warm nights on 
visiting such a corn field thousands of larvae might be found moving 
about. With the coming of dawn, however, all were again invisible 
having entered the corn stalks from which they had issued under cover of 
darkness, bored into fresh food if such had been found, or they had 
found places in which to hide during the day. 
To obtain information as to the extent of this migratory habit a series 
of 47 traps were placed in an experimental plot of about 1^ acres where 
corn of different types, flowers and vegetables were being grown and 
where larvae of the European corn borer were very numerous. The 
trap used consisted of a board 3 feet long by 4 inches wide, one long edge 
of which was sharpened so as to set firmly upright in the soil. A de¬ 
tachable cover was placed on top and extended about an inch on either 
side. Just under this cover strips of corrugated card board an inch wide 
were tacked to the side of the upright board. Migrating larvae finding 
this trap across their path and being unable to pass beneath the trap 
because it set in the soil had either to go around it or pass over it. If 
they chose the latter alternative they would find the corrugated card 
board and this being an ideal hiding place, they would remain. These 
traps were examined each morning where possible. In figure 5 the 
number of larvae found in all these traps each morning is shown graphic¬ 
ally. 
These traps were in operation from September 16 to October 14. 
During that time 1904 larvae were recovered from them, the greatest 
number of larvae on any one day being 186 and the greatest number from 
one trap for one day 23. The greatest number taken from one trap for 
the whole period was 223. The larvae caught in these traps must have 
been a very small per cent of the total number of larvae that were mi¬ 
grating but this information indicates that migration was very ex¬ 
tensive. 
The migration as indicated from a study of the records of these traps 
was greatest from corn which was overpopulated to flowers and vegeta¬ 
bles nearby but the movement was very general over all the cultivated 
area. 
