MEANS OP 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 in 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 

 l)y the Argentine ant, and probably the insects were first introduced 

 in the freight shipped chrect to these points from New Orleans oi- 

 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 establislmients 

 on shore. 



