AUTHOR’S ABSTRACT OF THIS PAPER ISSUED 
BY THE BIBLIOGRAPHIC SERVICE, JULY 12 
SEX DETERMINATION IN THE WHITE-FLY 
(TRIALEURODES VAPORARIORUM) 
FRANZ SCHRADER 
Columbia University, New York 
FOUR PLATES (THIRTY-SIX FIGURES) 
INTRODUCTION 
Parthenogenesis in the Homopteran family of Aleyrodidae has 
been known for some years. In 1903, A. W. Morrill, in the 
course of some breeding experiments with Trialeurodes vaporari- 
orum, found that all of the eggs laid by virgin females gave rise 
to males. Later, working with E. A. Back (’11), he discovered | 
that the same held true for Dialeurodes citri, another member of 
the same family. Both of these cases were reported from Amer- 
ica. In apparent contradiction to these conclusions, E. Har- 
greaves (’14), working on Trialeurodes vaporariorum in England, 
found that there only females emerge from eggs laid by virgin 
females. 
Recently, C. B. Williams (’17) confirmed Hargreaves’ obser- 
vations in regard to the English form, but while on a trip to 
America also found the reports of the American investigators to 
be correct, basing both of these conclusions on sex ratios obtain- 
ing in random collections. In England, these collections were 
made in various greenhouses, and of some 500 specimens ob- 
tained, only 23 per cent were males. The American collection 
was made in Virginia, and there 365 per cent of 254 specimens 
were males. My own collections, made in the vicinity of New 
York City, showed that the males constituted 464 per cent of a 
total of 403. These counts are a sufficient indication of the fact 
that the earlier observations in regard to parthenogenesis in the 
species are not erroneous and that the parthenogenetic behavior 
is different in the two countries.! 
'N.R. Stoll and A. F. Shull, Genet., vol. 4, in more extensive breeding experi- 
ments confirm the production of males from virgin females and find that the ratio 
of sexes in offspring from mated females is variable. 
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