MEANS OF DISPERSION. 21 
principal means of dissemination since they succeeded in establishing 
themselves. This is evident, as all the centers of infestation so far 
discovered, with the exception of those down the Mississippi River, 
the presence of which has just been explained, are located upon 
railway lines; in the Southern States, upon main lines running out 
of New Orleans. 
The ants are easily transported in packing and freight of various 
kinds. Large numbers of potted plants are shipped out of New 
Orleans to the surrounding country, and in many cases complete 
colonies of ants are sent with them in the soil surrounding the roots. 
Boxes and barrels of groceries, packing placed around fragile material 
to prevent breakage, and shipments of household goods may all 
contain queens and workers when shipped from infested points. The 
writer has observed a queen and many workers inside an empty 
passenger coach, which had been standing on the track for several 
hours during a rainstorm. 
The danger of promiscuous infestation is somewhat lessened by the 
fact that it is necessary for a queen ant to be transported with the workers 
in order that a new colony may be founded. In a large series of ex- 
periments conducted to determine this point we have never yet found 
any indication that the workers were able to produce eggs, or to 
reproduce their kind in any manner. Consequently large numbers 
of workers may be scattered broadcast over uninfested territory and, 
though they may live for a considerable time, they will ultimately 
die out if a queen is not present. It is probably due to this fact that 
these ants have not infested a great deal more territory than they 
have during the past 10 years, as it is a certainty that thousands 
of workers are being continually shipped from infested territory into 
uninfested localities. - At the same time the danger that fertile 
queens will be transported is considerable, for we have frequently 
found dealated queens foraging with the workers. The fertile queens 
will " take up " with any workers of the species, and it is only necessary 
for a queen and workers to be present iii a new locality in order to 
start a self -perpetuating infestation. 
Steamboats plying up and down rivers, carrying freight from 
infested points, are responsible for spreading great numbers of ants. 
For example, between New Orleans and Baton Rouge, La., there are 
over a hundred steamboat landings. These are nearly all infested 
by the Argentine ant, and probably the insects were first introduced 
in the freight shipped direct to these points from New Orleans or 
Baton Rouge. Many of the river steamboats are so heavily infested 
by permanent colonies of this ant that the workers are almost as much 
of a nuisance in the cook's galley as they are in culinary establishments 
on shore. 
