THE CITRUS WHITE FLY: LIFE HISTORY AND HABITS. 65 
structure, which act as sucking disks to aid the insect in reattaching 
itself. These protuberances are later withdrawn so that no trace of 
them remains. While becoming attached to the leaf the insect may 
be seen occasionally to rotate itself through an arc of 270°, in the mean- 
while frequently raising and lowering the abdomen. The cast skins 
are usually blown away by the breeze or fall from the leaf as soon as 
molted, but not infrequently are found partially pinioned beneath 
the body of the insects. Molting occurs most actively during hours 
of high humidity. Newly molted larvae are abundant during the early 
morning when the humidity ranges between 100° and 90°. 
FEEDING HABITS OP LARVyE AND PUP^E. 
As the white flies, or Aleyrodidae, belong to the Hemiptera, or 
sucking insects, the larvae and pupae do not eat the tissue of the leaf, 
but insert their thread-like mouthparts and suck the plant juices by 
the aid of a suction apparatus located in the head. Their ravages are 
not accompanied by any visible effect upon the leaf itself, but may 
be detected by means of the sooty mold which develops after the fly 
becomes very abundant. Our only means of estimating the amount 
of sap taken up by the insect is by the amount of waste material, or 
honeydew, ejected by it. A first-instar larva, on being watched under 
the compound miscroscope for 20 consecutive minutes with the tem- 
perature at 90° F., was seen to eject honeydew 48 times, or an average 
of about 10 times every 5 minutes. A pupa with well-developed eye- 
spots, in March, with the temperature at 85° F., ejected honeydew 
4 times in 5 minutes. This difference in the amount of honeydew 
secreted is due in part to the different temperatures at which the 
observations were made as well as to the difference in the degree of 
development. 
A very interesting observation on the amount of sap extracted by 
larvae and pupae of the white fly has been made by Dr. Berger * 
Leaves with live larvae and pupae were placed between glass plates so 
that the ejected honeydew was collected on the glass. By weighing 
it was found that each live insect had excreted about 0.0005 gram in 
48 hours. At this rate a tree infested with 1,000,000 white-fly larvae 
and pupae would lose one-half pound of sap per day. 
The Adult. 
The adult citrus white fly is very small, measuring only about one- 
sixteenth of an inch in length, and with a wing expanse of less than 
one-eighth of an inch. The natural color of the body, antennae, legs, 
and wings is entirely obscured by secretions of delicate white wax par- 
ticles, so that the insect appears snowy white (PL IX; text fig. 10, a-i) 
1 Bulletin 97, Florida Agricultural Experiment Station, pp. 63-64, 1909. 
59131°— Bull. 92—12 5 
