68 WHITE FLIES INJURIOUS TO CITRUS IN FLORIDA. 
CHANGES AFTER EMERGENCE. 
Immediately after emergence from the pupa case the adult differs 
from the more mature individuals in that the lemon-yellow color of 
the body is not obscured by the white waxy secretion that subse- 
quently appears. Also the wings, which appeared as crumpled 
whitish pads when the thorax was first protruded from the pupa 
case, have had time only to partially expand. As the fly crawls away 
from the case the wings are held perpendicularly above the back, but 
as the wrings gradually unfold and assume their normal shape they 
are lowered to their natural position. It requires, about 7 minutes 
for the wings to become straightened after the fly leaves the case, 
and from about 14 to 17 minutes from the time they first begin to 
expand. When fully expanded, the wings are colorless and trans- 
parent, with the costa pale yellowish. The pow T dery whiteness so 
characteristic of the flies as seen in the grove gradually appears as 
the wax glands secrete their particles of wax. In about one and three- 
fourths hours the wings and body have become perfectly white. 
CONDITIONS AFFECTING EMERGENCE. 
Aside from that inherent influence affecting the development of the 
citrus white fly and determining wiiether the adult shall emerge 
during the first or second general emergence period, as hereinafter 
described under "Seasonal history/' many field observations made at 
all seasons during the past three years, supplemented by laboratory 
experiments, have emphasized the great influence which temperature 
has on emergence. While a normal amount of humidity is necessary 
for emergence to occur, it is not so controlling a factor as temperature 
during ordinary Florida weather, as will be shown later. Light also 
seems to affect emergence under certain conditions. 
EFFECT OF TEMPERATURE ON EMERGENCE. 
Conclusions drawn from field notes, supplemented by laboratory 
experiments, show that emergence seldom occurs outside the range of 
62° F. to 85° F., with preference to temperatures ranging from 70° 
to 85°. During the winter months of December, January, and 
February, when the average monthly mean is about 60° F., no emer- 
gence occurs except to a slight degree during warm spells of several 
days' duration. In January, 1906, when the average monthly mean 
temperature was 59.6°, or practically normal, no flies w T ere noted on 
wing at Orlando, Fla., except in small trees beneath pinery sheds 
where the temperatures averaged several degrees higher than outside. 
During late December, 1908, and early January, 1909, the tempera- 
ture had been sufficiently high to cause a limited amount of new 
growth to appear on some trees in Orlando, and on January 4 a com- 
paratively large number of adult wiiite flies were seen feeding and 
