STATE PLANT BOARD
February 1943 ET-204
UNITED STATES DEPARTMENT OF AGRICULTUFE
Agricultural Research Administration
Bureau of Entomology and Plant Quarantine
AN INSECT SELECTIVITY CAGE FOR TESTING PLANT REPELLENCE
By E. W. Davis and G. T. York, Division of
Truck Crop Insect Investigations
A revolving cage used in experiments with repellent sprays
against the beet leafhopper (Eutettix tenellus (Bak.) and in deter-
mining the comparative aversion of this insect to different varie-
ties of sugar beets and beans has been described by Gillett and
Douglass. I This cage undoubtedly fulfilled the purpose for which
it was designed, but it had several disadvantages for selectivity
studies of the repellence of different tomato plants. Consequently,
a different type of selectivity cage was devised wherein only
leaves of the plants were used. This eliminated the necessity of
having the plants potted and the danger of losing the test plants
by disease. Also, only those leafhoppers that had actually selected
a leaf and were feeding thereon were counted, while those sitting on
the floor of the cage were ignored.
The machine consisted of the following three sections:
(1) A horizontal circular platform, 24 inches in diameter and 1
ino4 thick, mounted on a ball-bearing central pinion. The plat-
form made three turns per minute, the speed being governed by a
reduction gear, with power furnished by a small electric motor
(fig. 1). (2) On this platform was placed a sheet of 20-gauge
galvanized iron approximately 24 inches in diameter. Thirty half-
inch, numbered holes were punched equal distances apart about 3
inches inside the outer edge (fig. 2). (3) On the top rested a
bottomless celluloid cage 22 inches in diameter and 9 inches high,
with a hole in the middle of the top provided with a cork stopper.
Gillett, J. A., and Douglass, J. R. A revolving plant
cage for use in insect selectivity studies. U. S. Dept. Agr. Bur.
Ent. and Plant Quar., ET-139, 3 pp., illus. 1939. (Processed.)
The lower edge of the celluloid was faced with felt to prevent slip-
ping and to make the cage insect-tight.
In the use of the cage, a tomato leaflet was placed under each
hole of the galvanized sheet and held in place by a pad and adhesive
tape. The celluloid cage was put in place and the machine started.
The desired number of leafhoppers were inserted into the middle of
the cage through the hole in the top. Every 15 minutes a record was
made of the number of leafhoppers actually feeding at each hole. No
record was made of the leafhoppers sitting on the floor of the cage.
After each observation all leafhoppers were blown off the leaves.
Thus the number recorded at each observation was the result of new
selection and not an accumulation from previous observations.
In testing the efficiency of this selectivity cage, pads of
cotton moistened with 10-percent sugar solution were used instead
of leaves. The cotton pads were as nearly as possible the same size
and an equal quantity of sugar solution was used on each pad. Thus
feeding conditions were practically uniform within the cage. Results
from three tests showed no significant differences between the num-
bers feeding at any of the holes of the cage. When figured by the
chi-square method with n equal to 29, the P values were 0. 09, 0.12,
This cage has proved very satisfactory for demonstrating the
repellence of different tomato plants to the beet leafhopper, and
with any needed modification it could be used for other insects or
Figure l.-Rotating cage for testing samples of leaves for attrac-
tiveness or repellency. The motor is beneath the turntable.
STATE pLANT BOARD
Figure 2.-Top view of rotary platform, showing numbered holes
under which the leaf samples are fastened. The reduction
gear is shown at lower right.
UNIVERSITY OF FLORIDA
3 1262 09240 8961