84 
WHITE FLIES INJURIOUS TO CITRUS IK FLORIDA. 
of wintering-over pupae belong to the fourth, fifth, and sixth genera- 
tions, with the last two most abundantly represented. The number 
of third-generation pupae — or second generation should the first gen- 
eration in figure 11 not occur — to winter over is insignificant. 
Seasonal Fluctuations in the Numbers of Adults or so-called " Broods." 
During winters of unusual mildness there is a tendency for con- 
tinuous breeding, and adults in varying numbers can be found on 
the wing at different times, but these are as a rule too few in number 
to be of importance in effecting the general seasonal history of the 
citrus white fly. With the exception of the limited number of larvae 
developing from eggs deposited by these unseasonal adults, the 
white fly passes the winter in the pupal stage. The first general 
spring emergence of adults begins after the daily mean temperatures 
have risen to about 65° F., which at Orlando in 1909 was about Feb- 
ruary 20. 
There are three periods throughout the year when adult citrus 
white flies are so much more abundant than at other seasons that it 
is generally said there are three broods of white flies each year, 
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Fig. 12.— Diagram showing abundance of adults of the citrus white fly at Orlando, Fla., throughout 
1909. (Original.) 
although, as already noted under the subject of generations, the term 
brood in this case is somewhat misleading. The dates at which these 
adults appear is subject to such variation in groves in the same 
county, town, or even on individual trees of the same grove, that no 
accurate statement of the dates between which the broods occur 
throughout the State as a whole can be made. The authors, there- 
fore, have chosen to follow the history of the white fly in a single 
grove at Orlando during the season of 1909 as a specific example, as 
a basis, and present in figure 12 a curve representing the abundance 
of adults throughout that season. In all its essential features the 
curve is regarded as representing the appearance of adults in any 
grove, when it is remembered that variations of from one to three 
or four weeks may occur in the appearance of the broods. 
While it is generally believed that adults appear earlier in the spring 
throughout southern Florida, it is a fact that there is very little dif- 
ference in time of emergence between that and the central portion. 
Emergence throughout the northern portion of the State is, according 
to the season, from one to four weeks later than in the central and 
