38 
WHITE FLIES INJURIOUS TO CITRUS IX FLORIDA. 
Table VII. — Relative attractiveness to the citrus white fly of foliage of umbrella China 
trees and citrus trees. 
Observa- 
tion No. 
Date. 
Citrus trees. Umbrella China-trees. 
Number 
of 
minutes. 
Number 
of adults 
counted. 
1ST **«**■ 
Number 
of adults 
counted. 
Approx- 
imate 
number 
of leaves 
exam- 
ined. 
1 
2 
1909. 
Mav 18 
...do.... 
5 
5 
3 
5 
257 
19 
34 
52 
4 5 508 
6 5 615 
1 3 ! 477 
6 5 j 830 
25 
30 
6 
15 
3 
4 
June 11 
...do.... 
Total . 
18 
362 
17 IS 2,427 76 
In all, 2,789 specimens were counted, of which 88 per cent were on 
umbrella China tree leaves. It was estimated that in each record on 
a citrus tree approximately 2,000 leaves were examined, making 
34,000 in all. The individual leaflets composing the 76 umbrella- 
tree leaves numbered approximately 6,000. For practical purposes 
these leaflets are more comparable to the citrus leaves although the 
latter have on the average fully twice as much surface. With this 
basis for comparison it can be figured from the above data that there 
was about one adult white fly per 100 leaves on the citrus trees while 
there were about 40 adults per 100 leaflets on the umbrella trees. 
As has been indicated, the difference between the number of China- 
tree leaves in numbers 3 and 1 and between 4 and 2, respectively, 
represents the oldest spring growth, which was removed on May 24, 
leaving only a few growing leaves. No direct comparison was made 
between the attractiveness of the older growth of citrus and umbrella 
trees but apparently there is no striking difference between the two 
food plants in this respect. New watershoots were present on the 
citrus trees on both dates when observations were made but only in 
the case of one tree, 4 A, were many adults found on this growth. 
In observation No. 1 on the tree mentioned (4 A) 200 adults were 
counted on two watershoots. Except for watershoots there was no 
new growth on any of the citrus trees. 
At Orlando the umbrella trees usually start to put on new foliage 
in the spring before new growth appears on citrus trees. As a con- 
sequence China, and umbrella trees located near infested citrus trees 
receive large numbers of adults of the citrus white fly which migrate 
in search of attractive food. On February 22, 1909, the authors 
noted on the laboratory grounds that the shoots of the umbrella tree 
were beginning to put out new growth, the leaves not fully unfolded. 
The citrus white fly was found seatteriiigly on the umbrella leaves 
but on citrus trees specimens could be found only after careful 
search. 
