ET-186 October 1941
;TATF U-L-" '1 U'Onited States Department of Agriculture
Bureau of Entomology and Plant Quarantine
DETERMINING THE CATCHES OF CIGARETTE BEETLES
AND TOBACCO MOTHS MADE IN INSECT TRAPS
By R. W. Brubaker and H. N. Pollard, Division of Truck Crop and
Garden Insect Investigations I/
In conducting experiments with insect traps for the cigar-
ette beetle and the tobacco moth it was necessary to develop a
method of determining the catches of large numbers of these insects.
The culmination of the work at the Richmond, Va., laboratory with
traps since about 1933 resulted in the perfection of a suction-
light trap, which is now being operated in practically all tobacco
warehouses during the summer months. Reed et al., 2/ in describing
this trap, discussed a satisfactory method of determining catches
of the cigarette beetle. In 1940 some seasonal-history studies of
the tobacco moth and the cigarette beetle were undertaken with the
aid of these traps. The purpose of this paper is to give the de-
tails of some improvements in the method of determining the catches
of cigarette beetles and to describe a method of determining the
catches of tobacco moths.
Description of Apparatus
The equipment necessary for determination of trap catches
was as follows:
Anaesthetizing materials.--The insects were killed or ren-
dered inactive before determination of the catch was made. This was
accomplished by using a ball of absorbent cotton saturated with
chloroform or ether (fig. 1). The cotton ball was made by winding
1/ The authors are indebted to the following, who have done
some work at the Bureau's stored tobacco insect laboratory in Rich-
mond on determining the catches of cigarette beetles and tobacco
moths: W. D. Reed, E. M. Livingstone, A. W. Morrill, Jr., and
J. P. Vinzant.
2/ Reed, W. D., Morrill, A. W., Jr., and Livingstone, E. M.
Trapping Experiments for the Control of the Cigarette Beetle. U. S.
Dept. Agr. Circ. 356, 13 pp., illus. 1935.
cord ar:'.: a small quantity of acsor'-cnt cotton in such a manner as
to obtain a firm ball about 1-1/2 ii..ics in diameter. A piece of
the cord about 6 to 8 inches lc.-.P -.as left tied to it, and the
-:l-.I v..:- _.-nded in the co"erCc-, jar containing the insects. The
chloroform., or ether, was obtainable at wholesale drug establish-
L-rts. technical grade served satisfactorily for this work
These -:_ .- t-.tis -:
_...'_. ... 1L :,:arjtjp_ ,-e insects.--This apparatus con-
sisted of sieves -..c.,.'- lan'e r:.:,. for catching the material that
sifted thro '. i'- si.eves re -'-.i,..o'edi nIumbers 1, 2, and 3.
~..e screen-wire bottom of No. 1 was rc.de of hardware cloth having
8 meshes pcr inch, with a wire ':;-.:ter of 0.02 to O.C3 inch. The
scr-ri n in sieve No. 2 had 12 !:'-e. per inch, with a wire diameter
of 0.016 inch; and sieve No. 3 was ..me with screen having 20 meshes
por inch, with a wire diameter of 0.0135 inch, The openings in
!,:,. 3 were i~--. than O.Czc6 inch in width.
"'se sieves were nade by a l.-.l tinsmith. The screen wire
of the proper gauge C. some circular tin cako pans %'.'ere purchased
from a Lar&,are store. Tne t.ismith cut out the bottoms of the
c _; -and sold-,cd in the screens. The charge for labor in making
ii'- sieves in Richmond, Va,, :.'.- 50 cents each. The cost of ma-
terials for each sieve "as about cents. Figure 2 shows the com-
pleted set of sieves.
'._'i ,-:..'ces.--For determining large numbers of the in-
s-_cts a volumetric method v.as developed. The cigarette beetles were
measur.,-. in a lass graduate calibrated in cubic centimeters. For
deterimining iarge catches of to&'acco .roths a glass vial 1 inch in
diameter and -'-1/2 inches tall used. This \.s calibrated in
units of iCO0 moths, and when p:.&. rly filled it contained about
30 moths. Figure Z shows these measuring devices.
Determination of Catch
The following procedure vas used in obtaining recork.s of the
number of tobacco moths and ci.-r-ette 'rcc.tles caught in the traps:
'--r rI rf tnr.s.--The suction-light trars were operated
continuously (24 ho.urs per da."), and *r insects were collected at
about 7- .-,y inte"-'als. The glass jar containing the catch was re-
moved, :.!i.d, and replaced by a clean jar. The jas were labeled
for prL1,':r identification as to warehouse or storage section.
'. ~.- -',,'.l-t l.e .'.. ^ ci tch.--Before the insects
we,_- separated and countc.1, thr'-, were killed or anaesthetized by
inserting into the jars a ball of absorbent cotton saturated with
chloroform' and r-lacin:. the jar top) over the cord attached to the
ball (fig. 1). This confined the .v.1:ors of the anaesthetic in the
jar and held the cotton ball in suspension. A 10-minute exposure
in this manner rendered the insects inactive for a sufficient length
of time to determine the catch. Ether may be substituted satis-
factorily for chloroform in anaesthetizing the insects.
Separation of insects.--Removal of large moths, beetles, -.
other insects that were not stored-tobacco pests, but were sometimes
caught in the traps, was accomplished by sifting the catch through
sieve No. 1. Sifting the catch with sieve No. 2 permitted cigarette
beetles and other small insects or fragments to pass through, but
separated out the tobacco moths. The moths remaining on the screen
of this sieve were emptied into a pan, and the catch was detei;i.i.>d
by the method described hereinafter. The material that came through
sieve No. 2 was placed in sieve No. 3. This sieve permitted the
fine material, such as dust,, moth scales, fragments of insects,
etc., to pass through, but retained the cigarette beetles.
Counting or measuring.--The number of insects present in the
catch was determined by actual count or by measuring the volume.
When abc at 100 or fewer tobacco moths were caught, they were counted
individually, but if the catch was larger, the number was determined
by measure, the glass vial shown at left in figure 3, and previously
described, being used for this purpose. The determination of the
catch in this manner yielded results that averaged very close to
those obtained by actual counting. It was not practical to make
an actual count when thousands of insects were caught during one
The method of billing the vial was important in obtaining
accurate results. It was found that the measuring container held
about 800 moths when properly filled. The calibrated device ,"s
filled in the following manner: The tobacco moths were concentrated
in the receptacle, and the mouth of the vial was passed through the
catch of moths, scooping them up. The container was firmly tapped
once after each scoop, in order to get the proper density of moths.
When the container was filled in this manner, the total was a:-out
800 moths. When the catch was less than 800, the number was deter-
mined from the calibrated units of 100 moths.
The number of cigarette beetles was likewise determined by
counting when about 100 or fewer were in the catch. If the catch
exceeded this number, however, it was determined volumetrically.
The beetles were measured in the graduate shown at right in figure
3. As was determined by counting, 1,000 beetles occupied three
cubic centimeters. 2/ The total catch was determined by this
measure. The beetles were scooped up with the glass graduate in
the same manner as described above for moths. After each scoop
the graduate was firmly tapped once on a solid surface, which packed
the beetles to the proper density.
In a few instances there occurred in the catches large num-
bers of other species of beetles about the size of the cigarette
beetle, and the latter had to be counted. Except in a few in-
stances, however, the method described above proved satisfactory.
After the catch was determined, the moths, beetles, and all
other material were burned. It was important to destroy this ma-
terial to prevent reinfestation of tobacco, since some of the
adult insects were in a moribund condition from the effects of the
anaesthetic and would revive and escape.
Figure l.-Apparatus for anaesthetizing insects before determining
catches made in suction-light traps. The cotton ball was saturated
Figure 2.--Sieves used for separating insects caught in suction-light
traps. The screen in sieve No. 1 had S meshes per inch; in No. 2,
12 meshes per inch; and in No. 3, 20 meshes per inch.
Figure 3.-Calibrated measuring containers used in determining catches
of tobacco moths and cigarette beetles from suction-light traps.
The container on the left measured tobacco moths, and the one on
the right, cigarette beetles.
UNIVERSITY OF FLORIDA
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