448 
Journal of Agricultural Research 
Vol. XXX, No. 5 
In 1923 the plants were given a 
short day, beginning February 23, at 
which time the eggs were already 
hatching. By May 7 males and ovip¬ 
arous females had made their appear¬ 
ance, and the first eggs were deposited 
on May 22. In another experiment, 
beginning March 21, a plant with lice 
in the second generation was subjected 
to a short day, and by May 12 the ovip¬ 
arous females had made their appear¬ 
ance. 
THE TRUE SEXES AS INFLUENCED BY A 
LONG DAY 
According to the above experiments 
the production of the true sexes 
appears to be governed by the short 
days of the fall. How, then, would a 
daily light exposure of 15 hours or more 
act, and would the production of 
viviparous forms continue? To deter¬ 
mine this point, some strawberry 
plants infested with lice were placed out 
of doors September 4 and given 15 hours 
of daily light exposure by means of a 
60-watt electric light, which hung 
about 2 feet from the plants. At this 
distance the light did not raise the 
temperature of the air around the 
plants, as shown by several tests. A 
control plant was placed inside the 
laboratory, next to the window at 
the same time. On October 6 vivip¬ 
arous females made their appearance 
on the control plant, but were not yet 
present on the plants given the long 
day.' On November 5 eggs were found 
on the control. 
When examined on December 22, 
viviparous forms only were still present 
out of doors on the plants receiving the 
long exposure. However, the sexes 
did make their first appearance on 
January 4, 1924. This would indicate 
that a long day may successfully inhibit 
the formation of the true sexes, pro¬ 
vided a certain temperature level is 
maintained. The first 15 days of 
December averaged 40° F. and it is 
very likely that it was in this period 
that sex formation was initiated. In 
addition to a certain temperature 
level, possibly minimum temperatures 
may be factors. A minimum tem¬ 
perature of 28° on November 9 and 
10, and 20° on December 15 was re¬ 
corded. 
. Garner and Allard 2 have found that 
biennials will behave as annuals when 
subjected to a combination of long 
days and a lower temperature level. 
Lower temperatures alone would not 
accomplish this result. 
It should be noted that the straw¬ 
berry plants bearing aphids were given 
a long daily light exposure beginning 
September 4. The experiment was 
started early enough to insure if pos¬ 
sible against the production of the 
sexes. In 1922, strawberry plants 
were given a long daily exposure 
beginning October 12, and a few sexed 
individuals appeared two weeks later. 
This shows that once the tendency to¬ 
ward true sex production is initiated, 
it can not be done away with. How¬ 
ever, in the early part of September 
that tendency is still absent in Aphis 
forbesi in Tennessee. 
RELATION OF ANTS TO THE APHIS 
Sanderson 3 records that the ant, 
Lasius alienus , attends the straw¬ 
berry root louse in Delaware and 
carries it down to the roots of the 
plants, especially where the soil is 
sandy. In Tennessee various species 
of ants have been observed to care for 
the lice, but the species that is by far 
mostly commonly found is the little 
brown ant, Pheidole vinelandica , as 
determined by W. M. Wheeler. This 
species may be found about strawberry 
plants in March and up to January. 
Its method of tending the lice in order 
to obtain honeydew is interesting. 
Since the lice are most often clustered 
on the pedicels of the small, tender 
leaves, the ants protect them by 
building small craterlike mounds of 
dirt about the crown, so that the 
pedicels of the young leaves may be 
entirely covered and concealed from 
view, as shown in Plate 1, D. These 
little craters are often 2J/£ inches 
high, and sometimes completely cover 
the crown of the plant. In such cases 
lice may be found feeding on the 
crown of the strawberry. 
NATURAL ENEMIES 
The strawberry root louse will 
sometimes increase in numbers to 
such an extent that it becomes notice¬ 
able, but in most cases its natural 
enemies keep it in check. Several 
different species of these were bred, 
among them a^syrphid that had never 
been reported" as preying 4 upon the 
strawberry root louse, and an undeter¬ 
mined chalcid. Parasites were bred 
as late as December 14 and as early as 
May 14. Ladybird beetles, such as 
Hippodamia convergens and Coccinella 
novemnotato , were frequently found 
upon the root louse, as well as a larva 
2 Taylor, W. A. report of the chief of the bureau of plant industry. U. S. Dept. Agr. Ann. 
Rpt. 1922/23: 255-288. 1924. 
* Sanderson, E. D. the strawberry root louse. Del. Agr. Exp. Sta. Bui. 49: 1-13, illus. 1900. 
