THE CITKUS WHITE FLY: SPREAD. 49 
country or from grove to grove. At Orlando, in July, 1906, adult 
citrus white flies were observed late in the afternoon alighting on the 
sides of coaches and flying into the windows and doors of coaches 
of a passenger train standing at a railroad station (PL VI, fig. 3). 
Hundreds of adults were carried west toward Wildwood through 
points which, so far as known, were not infested at the time. The 
presence of China, umbrella, or citrus trees near railroad stations 
increases the chances for successful introduction by railroad trains. 
In this connection the recent action of the Atlantic Coast Line Rail- 
road and Seaboard Air Line Railway in destroying such trees along 
their right of way is to be commended. A map of Florida showing 
the distribution of the citrus white fly plainly indicates the relation 
between the railroads and the main lines of dissemination. This is 
shown in an incomplete way by figure 2, in which are given the points 
infested by the citrus white fly in Florida according to the records 
made in connection with the present investigation and such other 
records as are undoubtedly correct or which have been verified. The 
infestation at Arcadia, Fla., first discovered in January, 1907, but 
which probably resulted from an introduction of citrus white flies 
in 1905, was with little doubt due to the introduction of adult flies 
by means of railroad trains. An examination of the situation in 
February, 1907, by the senior author showed the center of infestation 
to be located near railroad stations, and careful inquiry concerning 
other possible sources showed that railroad trains were the most 
likely means of introduction. North of Arcadia no nearer infested 
point was known than Bartow and toward the south no nearer 
infested point than Fort Myers. The distance in each case was about 
40 miles. So far as known there were at that time no intermediate 
points infested between Arcadia and the two points mentioned. 
Here again the factors unfavorable to the successful establishment 
of the pest in a previously uninfested locality play an important role, 
as shown by the fact that even at the present writing the citrus white 
fly is not generally distributed between Bartow and Fort Myers. 
As we have no record and have heard no report of the occurrence of 
the fly at any other point than Arcadia, it is unlikely that other 
infested points exist. 
Steamboats are used quite extensively on the rivers and along the 
coast of Florida in transporting citrus fruits and have in a degree a 
similar status to railroad trains in transporting the citrus white fly. 
Citrus Nursery Stock and Ornamental Plants. 
The carriage of the citrus white fly in its egg, larval, and pupal 
stages by means of citrus nursery stock (PL VI, iig. 1) and ornamental 
plants has always been an important factor in the spread of the 
59131°— Bull. 92—12 4 
