Mar. 1, 1925 
The Strawberry Root Louse in Tennessee 
449 
of one of the Chrysopidae. Sander¬ 
son 4 records several hymenopterous 
parasites, among which are Lysiphlebus 
myzi Ashm., L. salicaphidis Ashm., 
Lygocerus stigmatatus Sag., and Adi - 
alatus densleonis Ashm. A louse at¬ 
tacked by parasites appears plump and 
greenish in color. As the parasite 
grows the body of the louse becomes 
much distended, and upon maturity 
nothing is left of the host except the 
straw-colored chitinous envelope. 
DIARETUS FUSCICORNIS ASHM. 
This little braconid (pi. 3, A) as 
determined by A. B. Gahan, was fre¬ 
quently bred from lice clustered on 
the pedicels of the leaves, and un¬ 
doubtedly helps to keep the lice in 
check. In color, it is shining black, 
legs yellowish, mixed with brown. 
Antennae of male 15-jointed, of fe¬ 
male 13-jointed. Length 1.6 mm. 
PARAGUS TIBIALIS 
This syrphid (pi. 1, E, F, G and pi. 
3, B, C, D) appears to be the most 
constant and efficient enemy of the 
strawberry root louse in Tennessee. 
The larvae were found in the field as early 
as April 18. A larva was observed to 
devour seven lice in five minutes in the 
laboratory. Larvae collected on May 20 
pupated May 22, and the adults emerged 
May 29. The puparium is inconspicu¬ 
ous on the under side of the leaves, and 
rather resembles a piece of dirt. 
Egg. —Chalk-white in color. In out¬ 
line, subcylindrical and ovate; trun¬ 
cated at the narrow end and rounded 
at the other. The surface of the egg 
is covered with very fine microscopic 
elevations arranged in lines, which 
under high magnification are seen to 
possess projecting arms, as shown in 
pi. 3, C. Length, 1 mm.; width, 0.40mm. 
Larva. —General coloring pale yel¬ 
low, mixed with patches of brown; 
posterior respiratory appendages dark 
brown at base, yellowish on apical 
third. Dorsal spiracular spine brown¬ 
ish. Surface of skin covered with 
minute, wartlike elevations. The 
spines on segment 4 appear equal. 
Beyond this segment the dorso-lateral 
spines are the longest, the dorsal 
spines small. Dorsal spiracular spine 
large, concave lateral, bifurcate. 
Length, 6 to 7 mm. Length of pos¬ 
terior respiratory appendage, 0.46 mm. 
Adult. —General coloring black, fre¬ 
quently reddish on the abdomen. 
Both male and f emale with a median black 
band on the face. Length, 3 to 5 mm. 
SUMMARY 
Since strawberries are classed as nur¬ 
sery stock in some States and required to 
be inspected for the strawberry root louse, 
Aphis forbesi Weed, it becomes necessary 
to determine more exactly its economic 
importance. Observation and experi¬ 
ments since 1919 show that Aphis forbesi 
is present in all the strawberry-growing 
areas of Tennessee and that it can not be 
classed as highly injurious in that State. 
It is not a leaf curler and apparently 
injects no toxin into the host plant. 
Plants were artificially infested with 
the root louse and kept so throughout 
the summer to determine the effects 
on the production of runners. These 
plants each produced an average of 
47.6 plants as compared with 49.7 
plants produced by the controls. 
Aphis forbesi passes the winter in the 
egg stage on the pedicels of the leaves. 
Hatching begins about February 15 and 
continues for about a month. Repro¬ 
duction continues viviparously through¬ 
out the summer and as late as Novem¬ 
ber. In Tennessee the lice remain 
mostly on the pedicels of the leaves and 
around the crown of the plant. Only 
rarely are they found on the roots. 
The ant, Pheidole vinelandica , is most 
commonly associated with Aphis forbesi. 
The true sexes first make their ap¬ 
pearance in October and may be found 
on the plants until February. 
In a study of the factors influencing 
the production of the true sexes in A. 
forbesi, it was found that the relative 
length of exposure to daily light ap¬ 
pears to be an important factor. By 
giving a daily short exposure of seven 
and one-half hours, beginning February 
23, the sexes made their appearance on 
May 7. Eggs were deposited on May 22. 
During the fall months of 1923 when 
the plants were given a long daily light 
exposure of 15 hours out of doors, the 
aphids continued to reproduce vivi- 
pariously as late as January 4,1924, when 
the first true sexes made their appearance. 
On the control plant the sexes appeared 
October 6. It is possible that a combi¬ 
nation of long days and a temperature 
of 50° F. or higher might have sufficed 
to keep the sexes from appearing. 
The strawberry root louse has many 
natural enemies, among the most im¬ 
portant of which is the little syrphid 
known as Paragus tibialis . Other nat¬ 
ural enemies include several species of 
Braconidae, the most common being 
Diaeretus fuscicornis. Several Cocci- 
nelidae and Chrysopidae may frequently 
be found preying on the lice. 
. 4 Sanderson, E. D. report of the entomologist. The strawberry root louse. Del. Agr. Exp. Sta. 
Ann. Rpt. (1899/1900) 12: 143-169, illus. 1901. 
