78 WHITE FLIES INJURIOUS TO CITRUS IN FLORIDA. 
large numbers and as frequently when males are not given access to 
them as do fertile females, and that the adults developing from these 
eggs are all males. Whether the adults from fertile eggs are invari- 
ably females has not been proved, although the evidence leaves little 
doubt that they are. If otherwise, it would be difficult to account 
for the fluctuations in sexes mentioned under the preceding heading, 
or to explain the great predominance of females over males after the 
species has become well established. 
INFLUENCE OF WEATHER CONDITIONS ON ACTIVITY OF ADULTS. 
During the cooler portions of the year, when adults are present on 
the trees, very few are seen flying about from tree to tree unless 
abundant. The morning and evening temperatures easily chill them; 
hence their activities are confined to the warmer part of the day. 
However, after summer weather has become established the white 
flies rest very quietly on the under surface of the leaves during the 
greater part of the day. They shun the bright sunshine and prefer 
leaves in shaded places. When exposed to the sun without protec- 
tion they soon die. As the temperature falls during the late after- 
noon, and especially after afternoon showers when the humidity has 
risen to 90° or even to 100°, they become very active, and about 4 
o'clock begin to fly about from leaf to leaf and from tree to tree, and, 
when very abundant, swarm in such large numbers about the groves 
and town streets as to arrest the attention of pedestrians, to whom 
they become at times a source of much aggravation, becoming en- 
tangled in the hair, crushed upon the clothing, breathed in with the 
air and causing choking, and flying into the eyes. 
FEEDING HABITS OF ADULTS. 
The adult insects, having well-developed sucking mouth parts, feed 
upon the plant juices in the same maimer as do the larvae and pupas, 
but with the advantages of not being confined to the same location. 
They do not leave any external evidence of the feeding except on 
very young growth, when the feeding of a large number of adults 
frequently produces a crinkling of the foliage. 
It is difficult to determine positively whether or not an adult citrus 
wliite fly is feeding when it is resting on a leaf or stem. Adults rest 
contentedly during the warm portions of the day upon the underside 
of leaves of plants upon which they have never been known to de- 
posit eggs. Under these circumstances they even appear to mate, 
and it seems probable that they feed to a limited extent. When on 
one of the principal food plants of the species, however, it is safe to 
consider that adults feed wherever eggs are deposited in noticeable 
numbers. It is because of this indiscriminate settling upon vege- 
tation upon which they are not able to subsist, and upon which they 
