f 
34 Journal of Agricultural Research voi. xiv, no . x 
and 21 infections were produced. The symptoms appeared in an average 
time of 26.4 days. From these data it is evident that the juice obtained 
by crushing virus-bearing aphids is virulent. 
TRANSFERS OF STRAINS OF APHIDS OBTAINED FROM OTHER STATES IN 
COMPARISON WITH TRANSFERS OF LOCAL, APHIDS WHICH WERE SUP¬ 
POSED NOT TO BE CARRYING THE SPINACH-BLIGHT VIRUS 
In some of the earlier experiments infections were produced when 
aphids which were supposedly not virus carriers were transferred to 
healthy plants. These led to the following experiment the object of which 
was to determine, so far as possible, the conditions which cause aphids 
to become virus carriers. In order to accomplish this, it was necessary 
to obtain strains of aphids from localities where, so far as is known, 
spinach-blight does not occur. Through the kindness of Dr. W. E. 
Hinds, Entomologist, Alabama Agricultural Experiment Station, a 
supply of Macrosiphum solanifolii on lettuce was obtained from Auburn, 
Ala. From Mr. Thomas H. Jones, Entomological Assistant, Truck Crop 
Insect Investigations, United States Bureau of Entomology, was obtained 
a large supply of Rhopalosiphum persicae collected on peppers in a green¬ 
house at Baton Rouge, La. Prof. C P. Gillette and Mr. L. C. Bragg, of 
the Colorado Experiment Station, furnished us with a splendid lot of 
eggs of R. persicae on peach twigs from Fort Collins, Col. Prof. J. R. 
Watson, Entomologist, Florida Agricultural Experiment Station, fur¬ 
nished several live individuals of R. persicae, among other species col¬ 
lected from Hibiscus sabdadriffa . 
As the various lots of aphids were received, they were placed, with the 
exception of a few individuals used immediately for experimental 
purposes, in cages on lettuce, eggplants, and healthy spinach. The 
aphids were allowed to feed and reproduce for several generations on 
the food plants mentioned until many thousand individuals of each 
strain were thus obtained. The eggs of Rhopalosiphum persicae were 
hatching at the time they arrived. The young stem mothers remained 
on the peach twigs until three generations of offspring were produced. 
The fourth generation was transferred to lettuce and healthy spinach. 
In this manner were obtained a sufficient number of aphids from widely 
separated regions, for use in comparison with local aphids collected in 
the vicinity of Norfolk, Va. Collections of local adult Macrosiphum 
solanifolii and R. persicae were made from diseased plants in the field. 
These were placed in cages on lettuce seedlings where they were allowed 
to feed and reproduce for five days. At the end of this period the adults 
were removed and destroyed. Some of the offspring were placed on 
other lettuce seedlings, some on eggplants, and the remainder on healthy 
spinach seedlings grown under insect-free conditions. The third week 
after the local aphids had been placed on the spinach seedlings some of 
these plants showed evidence of being diseased. Evidently they became 
