5i6 
Journal of Agricultural Research 
Vol. XXVU, No. 7 
injury might result. Matheson (75) records such a case in New York, 
where in 1915 1 f° r some unknown reason scarcely any of these (the 
third generation) produced winged forms, and as a result the trees 
became so infested that scarcely a leaf or fruit could be found that was 
not crowded with lice. If the factors involved in the early or late pro¬ 
duction of the winged migrants could be determined, this would be a 
long step in solving some problems in insect control. ” 
Jackson (jj, p. 541)1x1 a recent article takes up the effects of nutrition 
on morphology and cites several early workers, such as Kyber (1813), 
Keller, and Behr, who noted the appearance of winged male forms in 
aphids as a result of underfeeding. These authors do not go into detail 
in regard to the methods used. Of course the giving of a short day to 
a fxlant would be a method of underfeeding. 
EXPERIMENTAL DATA 
INFLUENCE of the short day on the production of sex forms 
The plapts used in the experiments were kept in pots and exposed _to 
from 7%. tp .8 hours, of light by being placed in a dark, ventilated chamber, 
the door pf which swings open from the top. The whole was kept in a 
screen-wire cage out of doors, where the temperature would not be 
materially different from that tinder natural conditions. The method 
u$ed tp subjejdt the plants, to a short day was to place the potted straw- 
beny plants with the lice in the dark chamber at 5 o'clock in the after¬ 
noon. The following morning at 9.30 the plants were removed and 
placed in the light. Gamer and Allard (6) showed in their experiments 
that the difference in temperature inside and outside the dark house 
was negligible, since the temperature inside was but 2 0 or 3 0 F. higher 
than the temperature outside; hence any responses on the part of the 
plants could not be attributed to lower temperatures. Single potted 
plants, were also darkened by having inverted over them a larger pot 
or a box. 
, Aphis forbesi Weed.—The first preliminary experiment was conducted 
with this species which is known as the strawberry root louse. On 
May 23, 1922, lice were placed on a potted strawberry plant, which was 
then given a short daily light exposure of hours. By September 18, 
males and oviparous females were present in large numbers. The first 
eggs were laid September 22, whereas normally the first eggs are laid in 
the field early in November. In Tennessee, egg laying continues, under 
natural conditions, through the month of December. 
In 1923, it was planned to start shortening the day to 7# hours as 
spon as tffe eggs were hatching, which began on February 16. From 
February 23, the plants bearing the aphids were subjected to the short 
day.. The first oviparous females were observed on May 7, and upon 
dissection yielded eggs. On May 22, eggs were deposited on the pedicels 
of the strawberry. 
Another plant taken from the greenhouse with aphids in the second 
generation was subjected to a short day, starting March 21, and by May 
12 oviparous females made their appearance. 
Aphis pomi DeGeer.—The green apple aphis passes its entire life 
cycle on the apple. The eggs hatched March 13, on a small apple tree 
und<er observation, two weeks before the buds burst, so that all of the 
young perished out of doors. A few of the eggs were saved, and, 
