THE CITRUS WHITE FLY: LIFE HISTORY AND HABITS. 57 
subjected to identical conditions of heat and moisture. Even when 
hatching was most concentrated during the heat of summer and 99.8 
per cent of the eggs hatched on the tenth and eleventh days from 
date of deposition, hatching extended over a period of from 9 to 19 
days. Hatching over a period of from 6 to 7 days after the first 
crawling young appears is an ordinary occurrence during the cooler 
portions of the season of activity. In this respect, white-fly eggs are 
markedly different from the eggs of most other insects deposited in 
batches which usually hatch within one or, at the most, a few hours 
of each other. 
PARTHENOGENESIS . 
The existence of parthenogenesis among aieyrodicls was first rec- 
ognized by the senior author * in connection with his investigations 
of the greenhouse white fly (A. vaporariorum) . His prediction at that 
time that this method of reproduction would ultimately be proved to 
occur among many if not all the species of Aleyrodes has been strength- 
ened by the results of the present investigations. While there are no 
definite data to the effect that parthenogenetic eggs are deposited 
under natural conditions, there is practically no doubt that such depo- 
sition does occur, especially by females not yet mated or by females 
appearing at unseasonable times or when males are decidedly in the 
minority. Scattered females emerging during the winter, or resulting 
from the comparatively few pupae surviving fumigation, either never 
have the opportunity to mate or deposit many of their eggs before 
such opportunity presents itself. 
That virgin females of A. citri, emerging from pupae kept separately 
in vials, and later confined in rearing cages under normal grove con- 
ditions, except for the exclusion of males, will readily deposit the nor- 
mal number of eggs, and that these eggs will develop normally and 
will produce adults of the male sex, has been thoroughly demonstrated. 
Of the five separate cage experiments started with parthenogenetic 
eggs, all of 111 adults emerging in four of the cages were males, while 
of 208 more adults emerging from the fifth cage, all but 4 individuals 
were males ; the 4 females emerging under such conditions as to lead 
to the supposition that they came from fertile eggs overlooked in 
preparing the leaf for the experiment. 
HATCHINCx. 
In hatching, the egg membranes rupture at the end opposite the 
pedicel, and then split down each side sufficiently to permit the 
young larva to crawl out. The glistening eggshell, somewhat resem- 
bling in appearance a bivalve shell, eventually becomes shriveled 
and loses its original form. 
1 Notes on Some Aleyrodes from Massachusetts, with Descriptions of New Species. 
Psyche, April, 1903, p. 81. Technical Bulletin No. 1, Mass. Agr. Exp. Sta., pp. 31-33. 
