PROGRESS REPORT ON" THE EUROPEAN CORN BORER 113 
of the moths recovered were gravid. During the period when this 
experiment was in progress the direction of the prevailing wind at 
the point of liberation was from the south and the southwest. This 
is believed to have influenced the flight of the moths in a general 
northerly direction, and may explain the failure to recover moths 
beyond the 1-mile limit at any other points of the compass. 
Although 5 miles was the maximum distance at which a stained 
moth was recovered in this experiment, it is believed that they are 
capable of dispersing to greater distances during a single flight, or 
in a series of flights, under favorable wind conditions. In the 
summer of 1922 a similar experiment indicated that adults were 
capable of flights of at least 20 miles over water. 
EFFECT OF NATURAL BARRIERS ON FLIGHT 
It does not appear that ordinary natural barriers such as high 
hills, densely wooded areas, or bodies of water, constitute any appre- 
ciable barrier to the flight of the moths. 
Although there is a tendency for the moths to disperse along val- 
leys and areas of low ground, they have also been observed in active 
flight on the tops of high hills. Cornfields situated on the tops of 
hills west and north of Boston, Mass., at an elevation of from 200 to 
400 feet, have in some instances been found to be infested to at least 
an equal extent with the cornfields on lower ground in the imme- 
diate vicinity. It is problematical whether the moths would be able 
to make flights over high mountain ranges. 
Relative to the efficiency of densely wooded areas as barriers to 
flight, in some instances fields of corn which were totally or partially 
surrounded by wooded areas were infested to a lesser degree than 
fields in the vicinity which were not so situated. This apparent 
protection, however, was by no means universal, as certain other 
fields situated amid similar surroundings were found to have an 
average infestation for the vicinity. In one case moths were ob- 
served in flight during the late afternoon among the trees between 
the open spaces of a wooded area, approximately 300 yards wide, 
which separated two large cornfields. It was not possible actually 
to trace individual moths through these woods from one field to the 
other, but evidently this strip of woodland was not acting as a bar- 
rier to flight. 
Judging from experimental observations, ordinary bodies of water 
do not act as barriers to the flight of the moths. During the progress 
of preliminary observations to determine this point, moths of both 
sexes were liberated from a boat during the daytime at a point in 
the center of a lake at Arlington, Mass. These moths, without excep- 
tion, flew rapidly with the prevailing wind toward the nearest shore, 
approximately 800 yards distant, and were soon lost to view. When 
moths were experimentally placed upon the surface of the water 
they rode the waves for a few minutes, but after a few struggling 
movements of the legs and wings they took flight in a normal man- 
ner. Moths which were experimentally plunged beneath the sur- 
face of the water immediately came to the surface and eventually 
took flight. When moths were liberated at the edge of the water 
during a strong offshore wind, about 15 to 20 miles per hour, they 
attempted to fly inland against the wind, but in almost every instance 
25411°— 27 8 
