PROGRESS EEPOET ON THE EUROPEAN CORN BORER 117 
older ones removed. These cages were in operation for an average 
period of 18 days, and during that period an average of only five 
males per cage were caught in the coating of sticky tree-banding 
material with which the surfaces of the cage and its support were 
covered, although large numbers of males were observed in the im- 
mediate vicinity. Most of the captured males were attracted to these 
cages within 24 hours after fresh females were added. During the 
progress of the flight experiments discussed in preceding paragraphs 
an attempt was made to recover the stained males by employing a 
similar cage but with negative results. 
DISPERSION 
The principal factor contributing to the long-distance dispersion 
of Pyrausta nubilalis is the transportation of infested plant prod- 
ucts or plant remnants. After the insect becomes established in an 
area local dispersion also occurs by means of flight or carriage of the 
moths, and in some instances through the drift of infested plant 
material in water. 
ARTIFICIAL DISPERSION 
Mention has previously been made of the probability that the 
European corn borer originally gained entrance to North America 
in shipments of raw broomcorn (fig. 2) from Italy and Hungary: a 
probability that was apparently confirmed when commercial ship- 
ments of this material, received at the port of New York during 
February and March, 1920, in April, 1922, and again in March, 
1923, were found by inspectors of the Federal Horticultural Board 
to be infested by P. nubilalis larvae. This occurrence illustrates the 
ease with which the insect may be transported for great distances, 
especially during its larval period ; and from what has already been 
stated concerning the ability of the larvae successfully to complete 
their development under adverse circumstances, it is apparent that 
at least a small percentage of the individuals contained in such 
material may transform to adults and start new infestations, pro- 
vided they are able to gain access to any of their many host plants. 
The great variety of plants infested by the insect, and its habits 
with relation to these plants, also contribute to the danger of dis- 
persion by common carrier. This danger is especially pronounced 
in the instance of the shipment of infested ears of sweet corn in the 
roasting-ear stage, corn on the cob, cornstalks used as packing 
material or otherwise, broomcorn (including all parts of the stalk), 
the stalks of all sorghums, and Sudan grass. In New England the 
plant products likely to be infested during certain periods of the 
year and which commonly enter commerce include, in addition to the 
above, celery, green beans in the pod, beets with tops, spinach, 
rhubarb, oat and rye straw as such or when used as packing material ; 
also cut flowers or entire plants of chrysanthemum, aster, cosmos, 
zinnia, hollyhock, gladiolus, and dahlia. In some instances larva? or 
pupae have been found in the cracks and crevices of boxes or other 
containers which had been used in shipping infested vegetables. 
These containers are permanent equipment of farmers and produce 
dealers, and are used in turn for shipping a great variety of vegetable 
products. Unless carefully inspected, they may serve as a means of 
dispersing the insect. 
