Fasten, Parthenogenetic Data. 
69 
More recently, F. M. Webster (’09), and S. J. Hunter (’09), 
on experiments with parthenogenetic eggs of Lysiphlebus tritico, a 
parasite on many Aphids, have brought forward data that appear 
to contradict Dzierzon’s contention. 
But in spite of these apparent exceptions, nearly all work on 
parthenogenetic development, amongst Hymenopterus insects, 
has confirmed the postulated view. However, as T. H. Morgan 
states it, “These cases serve as a warning not to insist with too 
much positiveness on the view that in the Bee unfertilized eggs 
always produce males, since they show that exceptions to such a 
rule may sometimes occur/’ 
(2). Aphids and Phylloxera. In the Aphids and Phylloxera 
we may likewise get parthenogenetic as well as fertilized eggs from 
the same female. The parthenogenetic eggs here give rise to 
males as well as to females, while the fertilized eggs produce 
females only. 
Leeuwenhoek, in 1695, and Reaumur in 1737, were the first 
investigators to observe cases of parthenogenesis among the 
Aphids. 
In the summer the Aphids produce generation after genera¬ 
tion of wingless parthenogentic females. When the fall approaches, 
a generation of winged males, and wingless females appear. After 
copulation, the females deposit, each, a number of winter eggs on 
the plant food, and from these, females arise during the spring, 
and lay parthenogenetic eggs. These develop and start the 
summer broods. 
Bonnet, in 1745, transferred Rose aphids to a green house 
before cold weather set in, and he observed nine generations of 
continuous parthenogenetic multiplication. Duval, observed eleven 
such generations in seven months. Kyber, in 1815, kept Aphids 
in a green house for four years, and found that all the individuals 
reproduced parthenogenetically, not a single case of sex-multipli¬ 
cation being discernible. 
All these facts seem to point to the conclusion that the change 
of temperature is the cause for the sexual cycle. Morgan, however, 
by subjecting Aphids to various changes of warmth and cold, was 
unable to induce a corresponding change in the mode of repro¬ 
duction. On closer study Morgan found that a great many indi- 
