THE BLACK FLY OF CITRUS. 9 
That this insect has been and is freely spread about on citrus nursery 
stock is shown by the fact that young lime trees in Ancon Nursery 
were found to be infested with it. Further numerous cases have been 
found in Panama where persons have grown young citrus trees of 
various kinds, mostly oranges and tangerines, in the city from seeds 
and then taken the plants, when they had grown to be a foot or more 
high, to their farms in the Las Sabanas region or to Taboga Island, 
which is 12 miles from the mainland in Panama Bay. Indeed, the 
heavy infestation on this island can not be accounted for in any other 
way except that infested food plants of the black fly were brought 
there from the mainland, and from these as a focus the insect has 
spread by natural means. Unquestionably the infestations at Mount 
Hope, Gatun, Pedro Miguel, Corozal, and Palo Seco were started in the 
same way. 
At Frijoles and Miraflores the infestations are in all probability 
"train borne." At the former place lime trees growing by the 
station and within 25 feet of the railroad track, which were carefully 
examined in October, 1918, and found to be uninfested, were found 
slightly infested in April, 1919. In the Canal Zone, the Panama 
Railroad supplying its commissaries runs its freight cars onto sidings 
bordered with limes infested with the black fly. This is particu- 
larly true at Ancon. Hence adults might readily fly onto or into 
such freight cars and fly off at a place like Frijoles where practically 
all trains stop. The only trees found infested in the region were 
five limes by the station ; large oranges and limes around the village, 
and younger limes at the entrance of the avocado plantation, both 
of which are at least 150 feet away from the railroad, being free 
from the pest. The same condition obtained at Miraflores, where 
two lime trees of a double row of 108 limes leading from the road 
west of Miraflores Tunnel to the filtration plant were found lightly 
infested. These trees were the two nearest the railroad and within 
75 feet of it. In traveling on the passenger trains from Panama 
City to various points along the main line, the writers and Mr. 
Molino have inspected the windows for the adults of Aleurocanihus 
woglumi, and although several species of larger insects have been 
found, at no time has a single adult of woglumi been seen. However, 
on such trips persons have been seen taking flowers and plants from 
Colon and Panama to points along the railroad in the Canal Zone 
or vice versa. The foregoing method may offer a possibility of the 
introduction of this insect into Florida from Cuba, as Newell (25) 
has pointed out. Whether the insects could become successfully 
established depends on the numbers of females that are introduced 
and whether or not these females have been fertilized. Its suc- 
cessful establishment in Florida will depend also on the adapta- 
