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ET-1EC9 December 1i
Unit'cd Stales Department of Agriculture
Eurcau o' Entomology and Plant Quarantine
IM?ROVENLn'7, IN THE STANDARD INSECT SWEEP NET
By W. C. Cco' nr,,':1 L. V,. Davis, Division of Truck Crop
a:,J Cardei Insect Investigations
Ihe sian,'arld -wcep net, with a circular opening about -
inches in diameter, has been used for collecting leafhoppers on "
beet leafhopper poioject ever since the wYork was started. Various
workers have recc'!.Ln., c-J the drawbacks of net collection as an
indicator of leafhoi:L,:cr populations, and other quantitative nietho.'
have been devised a: J used extensively, but the sweep net still
ceaiis 'he most rap..i .:-i-.od available, and efforts have been i. .W'e
to increasee its effici,.--y and reliability. Two improvements in
th3 wv~eep ne which ae been made at this laboratory during V..
ast t.,,o years are described below.
I. Moiification of the Net Frame for Sweeping Low Vegetation
The standard insect net has a round opening, and when v-':-
taticn a few inches in height is swept, only a small part of the
circumference of the nt opening comes in contact with the vI.L--
tation. During th, winter of 1938-39 the senior writer experim?!.ted
with various moLificat-'-ns of this round opening, finally produ'c-.: ;
a net frOMe that '.as nearly semicircular. It was found tL.at i -j
type of opening regularly secured larger numbers of leafhoj::-rs
than the ordinary circv.lar net, and that the collections tin-.kid t:
b& more uniform, btccaisc of the greater disturbance of the '.' -
The semioirc Fir frame is constructed by bending the ?
mct:ers of the fraD.- at :ight angles approximately 7- inchEs fi"...
the tips. The bend.'., is facilitated by heating the frame v.ith .
blc.;torch at the yoiit -.-where the bend is to be made. The temper of
the steel is altered at this point, but this seems to make little
difference in the strength of the frame, as such frames have been
in constant use for over a year without giving evidence of weakn:cs.'.
Figure 1 shows' the modified net frame and a standard '.::
frase without nets. The greater efficiency of the modified '.>t
frame for use cn lU.'.-gro'.'ing vegetation can be easily seen froi
II. An Improved Net Bag
The cloth bag originally used for sweeping work was made of
heavy cotton or light canvas material. Experiments with lighter
materials, performed by the senior writer and F. R. Lawson during
1930 and 1931, showed that some of these lighter materials could be
used to good advantage, and in recent years most of the nets used
have been made from cotton scrim or marquisette, which allows the
air to flow through the net. Air flow is of considerable import-
ance, as comparative tests have shown that a porous net will
capture at least twice as many leafhoppers as one made of material
so tightly woven that it seriously obstructs air flow. The chief
disadvantage of the more open materials is their tendency to catch
upon twigs and thorns, which tear the net or open up the threads
of the weave so that leafhoppers escape. This makes it necessary
to replace the net bags frequently, as one bag will seldom last for
more than two or three days of active service. The junior writer
suggested that net bags be constructed of two materials, the outer
or lower half of heavy cotton sheeting, and the upper or inner half
of marquisette. The half made of heavy cotton sheeting would come
in contact with the rough vegetation and the ground, while the
half made of marquisette would permit the free passage of air.
Such nets have been used for over a week of heavy duty without
showing any signs of wear, and they capture as many leafhoppers
as nets constructed entirely of open-weave material.
In constructing these nets the two materials are sewed to-
gether with a flat or "felled" seam, so that the net is reversible.
Figure 2 shows one of the net bags, and figure 3 shows the bag in
position on one of the modified net frames.
Figure 1.-The standard round sweep net frame and the
new semicircular frame.
Figure 2.-The new net hpg, made half of
cotton sheeting and half of marquisette.
Figure 3.-The nev net bag, it, po-
sition on a semicircular frame..
UNIVERSITY OF FLORIDA
II 21901 5III1i 1IIi111ii BIII Dil Ii
3 1262 09082 5034
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