March 1948 STATE PLAT BOARD ET-252
United States Department of Agriculture
Agricultural Research Admninistration
Bureau of Entomology and Plant Quarantine
BULK HEARING OF & MULTISTRIATUS MARSH.
AND RoPNUS I B ICH.
Charles L. Griswold,
Division of Forest Insect Investigations
In connection with research associated with the Dutch elm disease
control program, large numbers of Soltus multistriatus Marsh. (fig. 1)
Sand Hlurpijiu rufipes ERich. (fig. 2), the two principal vectors of
the Dutch elm disease fungus, Ceratostomella uA Buisman, were required
for experimental use throughout the year at Morristown, N. J. This was
especially true of 1. mltistriatus, the more important vector, in
testing the control value of DDT and other insecticides. Field-
collected material proved unsatisfactory, for it ms difficult to
obtain sufficient quantities, either in the proper developmental stage
or in pure cultures, A method uas finally adopted whereby adults of
both species were reared in the laboratory by artificially infesting
American elm wood under controlled conditions.
L room in the laboratory cellar ws especially constructed and
fitted with shelves to accom date a series of rearing containers.
Adequate heat was supplied throughout the year by hot-water radiators
connected with a coal-fired pot stove located just outside the room,.
Since both species of bark beetles are positively phototropic, electric
outlets were provided to furnish the lighting required for attracting
merging beetles to collection bottles.
Two types of rearing containers, differing principally in esize,
were employed. Although both could be used for rearing Scolytus Milti-
striatus. the smaller type (fig. 3) was easier to handle. In the
rearing of HBLuori2M rufies. however, the larger type was used.
The smaller rearing container (fig. 3) was fashioned from a
standard 5-gallon, open-top metal paint can with a recessed metal lid.
A narrow rubber gasket was glued to the under edge of the metal lid,
and a metal friction rim was applied over the closed edges of the can
and lid. To permit the attachment of a fixture for holding collection
bottles, and to admit light for beetle attraction, a hole 3 inches in
diameter was cut in one side, just above the center of the can. The
fixture consisted of the threaded metal cover of the bottle used for
the collection of beetles. Most of the cover was removed, and the
threaded rim remaining was attached over a 1-1/4-inch circular hole in the
center of a 4-3/8-inch disk of metal through which numerous holes
smaller than the beetles had been punched. The threaded rim was
attached to the metal disk by crimping the cut edge of the rim over the
edge of the large hole in the disk. In turn this assembly was fitted
over the 3-inch hole in the side of the can and held in place by a
circular metal band, 5/8-inch wide with an outside diameter of 4,-3/8
inches, riveted to the can. The beetle-collection bottles were of the
square, wide-mouth, screw-top type, 4-1/4 by 1-3/4 by 1-3/4 inches. They
were threaded so that they fitted into the fixture and could be fastened
tightly by a three-quarter turn.
The larger rearing container was made from an ordinary metal ash
can, approximately 24 inches in height and 15-1/2 inches in diameter, with
metal handles on the sides. A band of sponge rubber, arranged to fit
the rim of the can, was glued to the underside of a wooden cover.
Strong coil-wire springs attached to the metal handles and to the edges
of the wooden cover insured a tight fit. On one side of the can four
holes 3 inches in diameter were cut in a zigzag pattern from within a
few inches of the top to within a few inches of the bottom. Fixtures
similar to those used for the smaller type of rearing container were
fitted over these holes to hold beetle-collection bottles.
Scolytus nmltistr-atus Marsh.
Success in the reproduction of ScoLytus multistriatus in the
rearing room was dependent largely on the condition of host wood used
at the time of beetle introduction and on the temperature to which it
was exposed afterwards. Good results were obtained by the introduction
of beetles on partially seasoned wood only. Neither freshly cut wood
nor wood with very dry bark was found satisfactory. Beetles developed
satisfactorily at a temperature of about 780 F. and in a humidity
range from 50 to 60 percent-conditions that usually obtained in the
By the rearing methods outlined below, a good reproduction rate
was obtained, amounting in some instances to as high as 15 times the
number of beetles originally introduced, and a constant beetle supply
The technique was as follows
(1) Freshly cut sections of American elm, 3 to 5 inches in
diameter, were sawed into lengths of approximately 12 to 24 inches,
depending on the size of the rearing container to be used. The sections
were partly dried by exposing the shorter ones to a temperature of about
78 F. for 10 days, and the larger ones to the same temperature for 15
(2) The partly dried sections were placed in the rearing
containers in an upright position, care being taken not to obstruct the
fixture openings. The openings were closed temporarily with plugs.
(3) Beetles were introduced at the rate of 50 per square
foot of bark surface. The covers were placed on the containers and
allowed to remain there for 3 days to keep the interiors dark and thus
encourage an even beetle distribution throughout the containers.
(4) At the end of this time cloth covers were substituted
for the metal or wooden covers and allowed to remain for 5 weeks
to permit further drying of the bark.
(5) The cloth covers were then replaced with the original
covers. Since the beetles had usually begun to emerge by this time,
the plugs were removed from the insertion fixtures, and collection
bottles fitted in. Emergence continued thereafter for 4 to 5 weeks or
(6) Once emergence had begun, electric lights were used
during the day and turned off at night. The heat and light in the room
caused considerable beetle activity within the bottles, and since over-
crowding caused the beetles to injure each other, they were removed
from the bottles three or four times daily.
(7) Beetles that were not to be used immediately were trans-
ferred to other bottles of a similar type and size, into which some
material such as a folded filter paper had been inserted to furnish a
surface to which they could cling. These bottles, furnished with cloth
covers to provide aeration, were then stored in a cool, dark place. As
many as 400 beetles per bottle could be kept in good condition in this
manner for about 3 days.
Hyluropinus rufies Eich.
For the reproduction of Hylurgopins rufipes better results were
obtained by the use of larger pieces of host wood than were used for
Scolytus mnltistriatus. elm sections 4 to 5 inches in diameter and about
24 inches in length being used. Elm wood used for this species did not
require partial seasoning before beetle introduction. Seasoning was
required afterwards for about 4 weeks in the rearing room, however, and
during this period the cans were provided with cloth covers. The cloth
covers were then removed and replaced by the wooden ones, which were
used until emergence was completed. The wood in the containers was
infested at the rate of 100 beetles per square foot of bark area*
Since Hylurgopinus nies required a longer period for development
than Scolytus multistriatus progeny did not begin to appear in the
collection bottles until about 8 weeks after the parent beetles had been
introduced on host wood; but they often continued to emerge for 8 weeks
thereafter. As the adult beetles of this species did not injure each
other when crowded, it was unnecessary to remove them from the collection
bottles so frequently as the S. multistriatus. As a result the
emerging beetles, if not used at once, could be stored in the same
manner as &. multistriatus but in somewhat greater numbers per bottle
and for a slightly longer period.
In other respects the rearing methods and technique were similar
for both species.
Figure 1.-ScoLtus multistriatus adult.
Figure 2.-Hylurgoplnus rufipes adult.
Figure 3.--Smaller rearing container:
A, Unassembled; B, assembled.
UNIVERSITY OF FLORIDA
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