UBRARY 
 March 1948 STATE PLANT BOARD ET-252 
 
 United Statas Department of Agriculture 
 
 Agrieoltural Research Adninistration 
 
 Bureau of Entomology and Plant Quarantine 
 
 BUUC RBARINQ OF SOQLTrUS MULTI3TRIATUS MARSH. 
 
 AND Hn^JRGOPINUS RUFIPE3 EICH. 
 
 Charles L. Griswold^ 
 Division of Forest Insect Investigations 
 
 In connection with research associated vdth the Dutch elm disease 
 control progranv large numbers of Scolvtus mnltistriatns Marsh, (fig. 1) 
 and Hvlurgppinus rufipes Eich. (fig. 2), the two principal vectors of 
 the Dutch elm disease fungus^ Ceratostomella ulmi Buiaeuui, were required 
 for escperlmental use throughout the year at Morristown^ N. J. This was 
 especially true of S. multistriatus . the more important vector, in 
 testing the control value of DDT and other insecticides. Field- 
 collected material proved onsatisfactoxy, for it was difficult to 
 obtain sufficient quantities, either in the proper developmental stage 
 or in pure cultures, A method was finally adopted whereby adults of 
 both species were reared in the laboratory by artificially infesting 
 American elm wood under controlled conditions* 
 
 Rearing Room 
 
 A. room in the laboratory cellar was especiaUy constructed and 
 fitted with shelves to accomraodate a series of rearing containers. 
 Adequate heat was si^plied throughout the year by hot-water radiators 
 connected with a coal-fired pot stove located Just outside the room. 
 Since both species of baxic beetles are positively phototropic, electric 
 outlets were provided to furnish the lighting required for attracting 
 emerging beetles to collection bottles. 
 
 Rearing Containers 
 
 Two types of rearing containers, differing principally in size, 
 were employed. Althou^ both could be used for rearing Scolytus multi- 
 striatus. the smaller type (fig. 3) was easier to handle. In the 
 rearing of Hylurjgppinus rufipes. however, the larger type was used* 
 
 The smaller rearing container (fig. 3) iias fashioned from a 
 standard 5~g&llon, 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 acknit 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 l-lA-inch circular hole in the 
 center of a 4-3/6-inch disk of metal through irhich 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 i+-3/8 
 inches, riveted to the can. The beetle-collection bottles wore of the 
 square, wide-mouth, screw-top type, A-l/A by 1-3/A by 1-3/^ 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 hei^t and 15-1/2 inches in diameter, with 
 metal handles on the sides. A band of sponge rubber, arrangea zo 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 ins\ired 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. 
 
 REARING TECHNIQUE 
 
 ScoLvtus multistriatus 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 irtiich it 
 was exposed aften»ards. 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 developea 
 satisfactorily at a temperature of about 78o F. and in a humidity 
 range from 50 to 60 percent — conditions that usually obtained in the 
 rearing room. 
 
 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 
 was assured* 
 
 The technique was as follows t 
 
 (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 ten^Derature of about 
 
-3- 
 
 78® F, for 10 days, and the larger ones to the same ten^erature for 15 
 days. 
 
 (2) The partly dried sections were placed in the rearing 
 containers in an upright position, care being taken not to obstruct the 
 fijcture openings. The openings ?rere 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 
 allorred 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 pennit 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 
 longer. 
 
 (6) Once ^aergence 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 dally. 
 
 (7) Beetles that were not to be used immediately were trans- 
 ferred to other bottles of a similar type and size, into vriiich some 
 material such as a folded filter paper had been inserted to furni^ 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 40O beetles per bottle coiild be kept in good condition in this 
 manner for about 3 days. 
 
 Rvlurgopinus rufjpes Eich. 
 
 For the reproduction of Hvlurgopinus rufipes better results were 
 obtained by the use of larger pieces of host wood than were used for 
 Scolytus multlstriatus , 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 ronoved 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 beetj.es per square foot of bark area. 
 
Since Hylnrgoplnos rofipea required a longer period for development 
 thba. Scolytua multistriatua. progeny did aot begin to appear in the 
 collection bottles until about 8 weeks after the parent beetles had been 
 introduced on host nood; 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 
 ©merging beetles, if not used at once, could be stored in the same 
 manner as 3. nniltistriatus but in somewhat greater numbers per bottle 
 and for a slightly longer peilod. 
 
 In other respects the rearing methods and technique were similar 
 for both species. 
 
 Figure 1. — -ScolytuB multistriatus adult. 
 
 Figure 2» — Hylurgoplnua rufjpes adiilt, 
 
-5- 
 
 B 
 
 
 :i 
 
 Figure 3. — Smaller rearing container: A, Unassembled; B, assembled. 
 
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