THE BLACK FLY OF CITRUS. 19 
has been intimated by some writers that the black fly is an insect that 
can not be controlled except by such radical measures as were of 
necessity used in the eradication of citrus canker. 
Careful attention, therefore, was given this phase of the problem 
by the writers. In order to determine definitely the amount of 
injury done, numerous inspections and reinspections of trees were 
made. Daily observations were made for a year on a row of lime 
trees, and the condition of these trees in October, 1918, and April, 
1919, is shown in Plate II, figure 2, and Plate III, figure 2. Plate III, 
figure 1, shows the degree of infestation, which seemed to be at more 
or less of a standstill throughout this time, and there was practically 
no development of the black fly on these trees during the dry season. 
No appreciable injury was done to the trees during the year from 
June, 1918, to June, 1919. 
As a check on these lime trees an equal number growing thickly 
together in a hillside garden near the Board of Health laboratory was 
selected. Plates V and VI show the degree of infestation and here, 
because the trees were kept well shaded and protected from the 
drying winds by a large guava and were well watered at all times 
during the dry season, there seemed to be no checking of the develop- 
ment of the black fly at any time. 
However, while these trees showed some injury, i. e., a dropping of 
perhaps 5 to 10 per cent of their total number of leaves, they were 
far from being killed. Neither did the infestation of woglumi seri- 
ously interfere with the production of fruit on them. The infesta- 
tion, however, rendered the trees extremely unsightly. These trees, 
like those in Plate II, figure 2, and Plate III, figure 2, put forth an 
abundance of young growth with the coming of the wet season (from 
the middle of April to the last of June), and seemed to be outgrow- 
ing the woglumi infestation. 
In contrast with these two groups of limes is the young orange tree 
shown in Plate I. This is one of the few trees of this species that were 
readily accessible for daily observation. The degree of infestation in 
October, 1918, is shown in Plate I, A, and PI. IV, fig. 1. By the 
end of November, 1918, the infestation was very severe, the un- 
derside of every leaf being a mass of eggs and individuals in all 
stages of development. On the younger leaves it was estimated 
from counts that there were between 3,500 and 4,000 eggs per leaf, and 
when these began hatching the undersides were black with larvae just 
as if they had been dusted with soot. Due to this overcrowding on 
the part of the insects on the leaves there was unquestionably a heavy 
drain on the sap supply of the tree and when the dry season set in 
during the latter part of December, the tree began shedding its 
leaves, in spite of the fact that it was watered daily. The following 
is the apparent explanation of this defoliation : During the dry season 
