WHITE FLIES INJURIOUS TO CITRUS IN FLORIDA. 
INTRODUCTION. 
The present bulletin includes the principal results of studies of the 
two species of white flies most destructive to Citrus in the United 
States, commonly known as the citrus white fly (Aleyrodes citri ~R. 
& H.) and the cloudy- winged white fly (Aleyrodes nubifera Berger). 
With these pests successful control measures must be based on a 
complete understanding of the insects themselves. On this account 
the study of the insects, their life history, seasonal history, habits, 
food-plant relationships, and related topics has occupied an unusually 
important position in the white-fly investigations. 
The authors have concluded that unless natural enemies capable 
of controlling the two white-fly pests are existent and are secured,, 
control measures will require permanent expert supervision for the 
most satisfactory and economical results — not supervision of work in 
individual citrus groves, but supervision aimed principally to prop- 
erly correlate individual efforts and to take full advantage of favoring 
local conditions. For supervision of this nature, a good foundation 
of extensive and reliable studies of the insects is necessary. While 
the portion of the white-fly investigations herein reported is com- 
paratively extensive, it is necessarily not exhaustive and in the 
course of time certain features of this work can undoubtedly be con- 
tinued with profit as an aid to the future improvement of control 
measures. 
The white-fly investigations now in progress were begun in July, 
1906, by the senior author, who was in field charge up to the time of 
his resignation from the bureau in August, 1909, The junior author's 
connection with these investigations dated from June, 1907. The 
life-history studies of the first two years have been largely superseded 
by the more extensive work of the third year. Practically all of the 
data presented under the subjects of the life history and habits and 
the seasonal history of each species are based on studies by the junior 
author and were written by him. The remainder of the bulletin was 
written by the senior author. 
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