Humble, Leland M.

English

Journal of the Entomological Society of British Columbia

J. ENTOMOL. SOC. BRIT. COLUMBIA 102, DECEMBER 2005  81  SCIENTIFIC NOTE A novel host association for Monarthrum scutellare (Coleoptera: Curculionidae: Scolytinae) in British Columbia LELAND M. HUMBLE1  Monarthrum scutellare (LeConte) is an ambrosia beetle that ranges from British Columbia to northern Baja California in Mexico (Bright and Stark 1973, Wood 1982, Wood and Bright 1992). It is re-corded to breed in various species of Fa-gaceae including Chrysolepis, Lithocarpus densiflora (Hooker & Arnold) Rehder, Quercus spp., Quercus agrifolia Neé, Q. garryana Douglas and Q. kellogi Newberry (Farris 1965, Bright and Stark 1973, Bright 1976, Wood and Bright 1992) with single records from Abies and sequoia that Bright and Stark (1973) considered accidental or erroneous. On 2 May 2005, a 38-cm length of “green” split alder firewood and associated Scolytinae (Coleoptera: Curculionidae) collected from a recently delivered com-mercial load of firewood were submitted to the Canadian Forest Service for identifica-tion after beetles were observed emerging from the wood. The half stem section was split off-centre, included all annual growth rings, and was 18.2 cm in diameter and 27 years of age. No bark was present on the piece of firewood, however, a single V-shaped parental gallery 22 mm in length was incised in the sapwood and five adult Alniphagus aspericollis (LeConte) (Curculionidae: Scolytinae) were associated with the sample. The gallery shape agrees with those described by Bright and Stark (1973) as typical for A. aspericollis. The presence of a parental gallery of A. asperi-collis and the structure of the wood (absence of rays, ring porous wood) con-firmed that the host attacked was Alnus rubra Bongard (Betulaceae). Boring dust was being actively extruded from ambrosia beetle galleries along the split face of the wood; however, no en-trance holes were observed on the outer face of the bole. The wood was held at room temperature for adult emergence and 52 female and 55 male M. scutellare emerged between 2 May and 17 May 2005. The sample was then split longitudinally and the distribution of galleries along the split face enumerated by growth ring and growth ring widths measured to the nearest 0.5 mm. All of the 22 M. scutellare galler-ies visible on the split face were in the wid-est growth rings (mean ± SD = 5.6 ± 0.99 mm) from the first nine years of growth. No galleries were apparent in the outermost 40.5 mm of the xylem comprising the last 18 years of growth.  A band saw was used to cut 1-2 cm thick cross-sections containing ambrosia beetle galleries and the galleries dissected. Bifurcations were evident in four of the five partial galleries dissected, with three having a single bifurcation and one bifurcating twice. The galleries dissected (longest arm) ranged from 12.5 to 52.8 mm in length and were heavily stained black, likely by the ambrosia fungus introduced by the female beetles (Farris 1965). Although larvae of Monarthrum species, including M. scutel-lare (Wood and Stark 1973), M. mali (Fitch) and M. fasciatum (Say) (Solomon 1995) characteristically develop in “cradles” excavated above and below the sidewalls of the parental galleries, no brood cradles were evident in the dissected galler-ies or on the radial faces of the split wood. While no evidence of brood production was found during gallery dissections, the heavy staining observed along the length of the dissected galleries indicates that the ob-served attack was not recent and the large 1 Natural Resources Canada, Canadian Forest Service, 506 West Burnside Road, Victoria, British Columbia 82  J. ENTOMOL. SOC. BRIT. COLUMBIA 102, DECEMBER 2005   numbers of adults recovered suggests that M. scutellare can attack and breed in red alder. At least one oak-feeding species of Monarthrum, M. laterale (Eichhoff), has been recorded from alder and M. biden-tatum Wood, M. hoegi (Blandford) and M. umbrinum (Blandford) breed in Alnus spp. (Wood 1982, Wood and Bright 1993). Thus, while M. scutellare is usually associ-ated with species of Fagaceae, it is possible that hosts in other families may also be util-ized. Alternatively, the emergent adults could represent mature adults attempting to establish brood in the firewood piece. Be-cause galleries associated with this collec-tion were incomplete, the ability of M. scutellare to develop in A. rubra cannot be determined with certainty. The presence of brood production in choice and no-choice breeding trials of M. scutellare in cut stem sections of native Fagaceae (Quercus gar-ryana Douglas ex Hooker) and A. rubra or the discovery of brood in naturally attacked red alder will be necessary to confirm breeding in non-traditional hosts. Although evidence of breeding of M. scutellare in red alder is currently circumstantial, such novel host associations have been demonstrated to occur in other ambrosia beetles. Nijholt (1981) reported attack in red alder by two species of ambrosia beetles, Gnathotrichus retusus LeConte and Trypodendron linea-tum (Olivier), which normally utilize conif-erous species as hosts (Bright 1976, Wood and Bright 1992). Kunholz et al. (2000) subsequently confirmed red alder as a breeding host for G. retusus, while Lindgren (1986) documented brood produc-tion by T. lineatum in bigleaf maple, Acer macrophyllum Pursh.  Voucher specimens of A. aspericollis and M. scutellare have been deposited in the reference collection at Canadian Forest Service, Pacific Forestry Centre, Victoria, British Columbia. L. Safranyik, T. Shore and A. Carroll, Natural Resources Canada, Canadian Forest Service reviewed an earlier version of this manuscript. Their helpful comments and those of two anonymous reviewers are gratefully acknowledged. REFERENCES Bright, D.L. 1976. The bark beetles of Canada and Alaska Coleoptera: Scolytidae. Canada Department of Agriculture Publication 1576. Ottawa, ON.  Bright, D.L. and R.W. Stark. 1973. The bark and ambrosia beetles of California Coleoptera: Scolytidae and Platypodidae. Bulletin of the California Insect Survey 16: 1-169. Farris, S.H. 1965. Repositories of symbiotic fungus in ambrosia beetle Monarthrum scutellare Lec. (Coleoptera: Scolytidae). Proceedings of the Entomological Society of British Columbia 62: 30-33. Kuhnholz, S., J.H. Borden, and R.L. McIntosh. 2000. The ambrosia beetle, Gnathotrichus retusus (Coleoptera: Scolytidae) breeding in red alder, Alnus rubra (Betulaceae). Journal of the Entomological Society of British Columbia. 97: 103-104. Lindgren, B.S. 1986. Trypodendron lineatum (Coleoptera: Scolytidae) breeding in big leaf maple, Acer macrophyllum. Journal of the Entomological Society of British Columbia 83: 44.  Nijholt, W.W. 1981. Ambrosia beetles in alder. Canadian Forestry Service Research Notes 1: 12. Cana-dian Forest Service, Ottawa, ON. Solomon, J.D. Guide to insect borers of North American broadleaf trees and shrubs. U.S. Department of Agriculture, Forest Service, Agric. Handbk. 706. Washington D.C. Wood, S.L. 1982. The bark and ambrosia beetles of North and Central America (Coleoptera: Scolytidae), a taxonomic monograph. Great Basin Naturalist Memoirs 6: 1-1163. Wood, S.L. and D.E. Bright. 1992. A catalog of Scolytidae and Platypodidae (Coleoptera), Part 2: Taxo-nomic Index. Great Basin Naturalist Memoirs 13: 1-1553. 

A novel host association for Monarthrum scutellare (Coleoptera: Curculionidae: Scolytinae) in British Columbia

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A novel host association for Monarthrum scutellare (Coleoptera: Curculionidae: Scolytinae) in British Columbia

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Journal of the Entomological Society of British Columbia