THE CITRUS WHITE FLY: LIFE HISTORY AND HABITS. 77 
old leaf of orange for two hours, when the adults were removed and 
576 eggs were found to have been laid on the tender leaf and but 25 
on the old leaf. Again, under practically the same conditions, 364 
eggs were deposited upon tender growth and but 2 on very old growth. 
The difference between oviposition on tender August growth and 
spring growth is not as great as this, though very marked, as about 
90 per cent of the third-brood adults fly to the new growth put on 
by the trees late in July and early in August. 
From the foregoing it is evident that the number of eggs deposited 
is strongly influenced by the nature of the insect's food. Females 
confined in empty cages never deposit eggs, neither do those resting 
upon thick bark, ladders, or picking boxes, and, as has been stated 
under "Food plants," oviposition is entirely checked 1 when females 
are confined with leaves of nonfood plants. This difference in the 
number of eggs deposited on various plants may prove of value from 
the standpoint of trap foods, and become a factor in the control of 
this pest. 
PROPORTION OP SEXES. 
Examination of thousands of adult citrus white flies at all seasons 
of the year has shown that after a grove has become well infested an 
equilibrium between the proportion of males and females is estab- 
lished from which there is under ordinary conditions little variation. 
In such groves it has been found that from 60 to 75 per cent of the 
adults are females. Of the records on file, about 66 per cent give 
percentages of 60 and over for females, while 66 to 76 per cent are 
more frequent percentages where adults are abundant. 
In groves where the progress of the white fly has been very seri- 
ously and suddenly checked by natural or artificial causes, the pro- 
portion of sexes is subject to a much wider variation and there follow 
for a time fluctuations between a predominance of males and females. 
In one such grove where the white fly had been greatly reduced in 
numbers because of the scarcity of adults of the first brood, there was 
a very large percentage of males appearing with the second brood, 
which in turn resulted in the third brood of 90.5 per cent females. 
In a second grove, where over 99 per cent of the white fly were killed 
by fumigation, the few females of the first brood, because of their 
isolation due to scarcity in numbers, were forced to deposit mostly 
infertile eggs, which resulted, in the second brood, in a reduction of 
females to 18.6 per cent. 
Dependence of sex upon parthenogenesis. — The proportion between 
the sexes is largely and evidently entirely dependent upon partheno- 
genesis. It has been shown that infertile females deposit eggs in as 
1 Three hundred adults of A. citri confined on the tenderest spring growth of oak 
for three days deposited 1 egg. 
