'ATE september 1952 ET-304
United States Department of Agriculture
Agricultural Research Administration
Bureau of Entomology and Plant Quarantine
A FRAMELESS INSECT CAGE FOR USE ON TREES
By Robert Z. Callaham and John M. Miller
Division of Forest Insect Investigations
The frameless cage described herein was constructed and used for
caging bark beetles on the basal 10 feet of small trees. Most of the
trees were 12-14 inches in diameter, but some were as large as 24
inches. The primary advantages of this cage are: (1) It costs less and
is easier to install than a frame cage; (2) there is no problem of sealing
the cage to make it insect tight; and (3) off-season storage of the cage
requires a smaller area than that needed for frame cages.
This frameless cage can be made to cover any portion of a tree or
other elongated object by varying the number and length of the sections
of screen that are fastened together. It can be made with a flap at the
bottom, which can be closed in the same manner as the top and thus
permit the caging of any desired portion of the tree, or the lower flap
can be buried in the ground.
The cage may be made of either plastic or metal screen. Plastic
screen has the advantages of being light in weight, not subject to mois-
ture damage, and of having only a negligible effect on the environment
in the interior of the cages. On the other hand, metal screen is cheaper
and provides more rigidity, thereby facilitating installation and elimi-
nating the need for supporting wires or hoops.
Both the plastic and metal cages are fabricated on the same general
plan from strips of screening eut to any desired width or length. The
plastic cage has both top and bottom flaps made of the same material, but
the top flap of the metal cage is of canvas.
Figure 1.--Pattern for a frameless plastic-screen cage.
a. Zipper halves.
b. Pocket for hoop wires made with
a single row of stitches.
c. Double row of stitches.
d. Supporting wires.
e. Single row of stitches to prevent
unraveling of screen.
A pattern for the plastic cage is shown in figure 1. First, the strips
of screening are joined along the selvage by two parallel rows of stitches
with cotton thread. If 28-mesh screen is used, no additional support is
needed on the seams, but with screen of larger mesh it may be necessary
to back the seams with cloth tape or webbing. Second, cross-pockets 1
inch deep for insertion of wire hoops are made with a single row of stitches,
and another row of stitches is made across the top and bottom of the cage
to prevent the screen from unraveling. Finally, two zipper halves are
sewed in place on the sides of the cage.
The construction of a metal cage requires only a slight modification
of the pattern shown in figure 1. The only tools needed are a hammer,
brace and bit, and a heavy-duty stapler. The lengths of screen are
nailed together along the selvages between two wooden cleats that are
1/2-inch thick, 1-inch wide, and about 6 inches shorter than the screen.
For closing the cage, holes for 1/4-inch carriage bolts are drilled at
regular intervals in two other cleats, which are nailed to the free sides
of the cage. A strip of canvas is stapled to the upper edge of the screen
to form the upper flap.
This cage can be easily installed. Two men work with 10-foot ladders
on opposite sides of the tree. Approximately 2 man-hours are required
for the installation of each type of cage.
The first operation is to smooth the bark with a drawknife where the
top of the cage is to be placed. A strip of cotton batting 3 or 4 inches
wide is placed around the tree at this point and tied with string. Then
the cage is wrapped around the tree and, if it is a plastic cage, the
supporting wires (Nos. 14 and 15 wire) are fastened to the lower limbs
or to the tree trunk above the upper closure and the zipper closed. If
it is a metal cage, the carriage bolts are passed through the holes in
the cleats and fastened. The ends of the hoop wires in the plastic cages
are looped over one another to keep the cage away from the tree. The
upper flap of the cage is gathered around the tree and tied in place on
the cotton batting with two or three lengths of string to prevent the
escape of bark beetles. This flap and cotton-batting technique can be
used to make a similar closure at the bottom of the cage, or dirt can be
placed on the lower flap.
To place insects in the cage, one can remove a small portion of the
dirt, lift the flap, place the insects on the ground inside the cage, and
replace the dirt on the flap. Sometimes a log containing bark beetle
broods is wired to the tree within the cage.
Installation of both types of cage, with logs containing bark beetle
broods, is shown in figure 2.
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One man can easily dismantle and roll up one of these cages in 10
minutes by the following steps: (1) The supporting wires and upper flap
ties are cut; (2) the side closure is opened; (3) the hoop wires are un-
fastened and straightened; and (4) the cage is rolled for storage (fig. 3).
Nine or ten of these cages can be stored in a space 10 by 3 by 2 feet.
Figure 2. --Cages installed on basal portions of small pines.
Figure 3.--Plastic (upper) and metal (lower) cages ready for storage.