Buchananius sulcatus, (LECONTE)

Prena, Jens, Steiner, Warren E. & Grebennikov, Vasily V., 2014, Buchananius sulcatus (Leconte) (Coleoptera: Curculionidae: Baridinae) Reared from the Fruiting Bodies of the Ascomycete FungusTrichoderma peltatum (Berk.) Samuels, Jaklitsch, and Voglmayr in Maryland, USA, The Coleopterists Bulletin 68 (3), pp. 399-402 : 399-401

BUCHANANIUS SULCATUS (LECONTE) ( COLEOPTERA : CURCULIONIDAE : BARIDINAE ) REARED FROM THE FRUITING BODIES OF THE ASCOMYCETE FUNGUS TRICHODERMA PELTATUM (BERK.) SAMUELS, JAKLITSCH, AND VOGLMAYR IN MARYLAND, USA

JENS PRENA Mühlendamm 8a 18055 Rostock, GERMANY baridinae @gmx.de

WARREN E. STEINER, JR. National Museum of Natural History , Smithsonian Institution, MRC 187 Washington, DC 20013-7012, U.S.A. [e-mail]

AND

VASILY V. GREBENNIKOV Canadian Food Inspection Agency, K. W. Neatby Bldg., 960 Carling Ave. Ottawa, ON K1A 0Y9, CANADA [e-mail]

While collecting beetles associated with dead wood and fungi at the Patuxent Research Refuge in central Maryland, USA on 11 August 2012, WES noted a “series of tiny baridines on a puffballlike tan fungus on fallen beech branch” in a large tract of mixed mature forest. At least 20 of the weevils, including several mating pairs, were observed on, and appeared to be feeding at, the surface of two globular fruiting bodies, indicating a possible host association. Several were collected along with a small sample of the fungus, leaving the rest intact for later study. The weevils, Buchananius sulcatus (LeConte) , were identified by JP with great interest, since no definite association had been confirmed among fungi and any group of “higher weevils” except for wood-boring Scolytinae and Platypodinae .

The beech ( Fagus grandifolia Ehrh. ; Fagaceae ) log with the fungus was a section of a large, dead canopy branch that had fallen approximately one year prior to being found. The adjacent dead standing trunk, at the bank of a stream, had been killed by girdling by beaver. The log, 3.5 m in length and 2–3 dm diameter, was embedded at one end in sandy soil and leaf litter ( Fig. 1 ); most bark was still intact and studded with polypore sporocarps ( Daedaleopsis confragosa (Bolton) J. Schröt., Stereum complicatum (Fr.) Fr. , and Stereum ostrea (Blume and Nees) Fries ) and patches of Biscogniauxia atropunctata (Schwein.) Pouzar (Xylariales) . The two stromata on which the weevils were found were ca. 5 and 7 cm wide and 2–3 cm in thickness, with the larger stroma on the top of the log and the smaller one located on the side, near the soil at the half-buried end. Weevils were found only on the stromata and on bark within a few centimeters away, and not seen on the other fungi. The stromata were initially identified as Hypocrea peltata Berk. (Ascomycota) , now known as Trichoderma peltatum (Berk.) Samuels, Jaklitsch, and Voglmayr (Jaklitsch and Voglmayr 2014).

The stromata were examined on 22 August and showed little change in appearance; many single and pairs of weevils were again observed and another small piece of the fungus was taken for a dry sample. On 29 August, fewer B. sulcatus were seen and the stromata were “still moist, rubbery and not larger” and small “push-outs” of whitish insect frass were seen on the surface. A piece (4 × 3 × 3 cm) of the larger stroma was cut off and kept in a clear plastic vial for observation; a few small, white, c-shaped beetle larvae were exposed at the cut in cells in the tissue just beneath the surface, not in the tissue of the interior, and more were dissected out and preserved in 95% ethanol. During the next days, more larvae were found at the bottom of the vial, having exited the fungal tissue; these were allowed to burrow into sandy moist soil in the event they were to pupate. The drying fungus sample taken on 22 August began to show evidence of the same larval infestation, with granular white frass in small clumps, one bearing a larval head capsule exuvia.

On 9 September, the larger stroma was found detached from the log but resting on it, showing more evidence of larval feeding ( Fig. 2 ); it was kept in a plastic container with a few additional larvae emerging over the next five days, then no more. The sample began to darken and was frozen, then preserved in ethanol. Upon examination later, three larvae of an undetermined species of Ampedus Dejean (Elateridae) were found inside cavities in the base of the stroma, and two more presumed B. sulcatus larvae in cells close to the surface. The second smaller stroma was found “melted down”, detached and decayed on the soil, with no weevils or larvae present. However, two additional small stromata were discovered among Stereum brackets on the upper end of the log; these appeared firm and with larval frass clumps on the surface and larvae inside, with two weevils hiding near the base.

Adult B. sulcatus started to emerge on 3 October, 34 days after the first larvae had entered the soil. The rearing chamber was examined immediately for immature stages, but all specimens had completed metamorphosis by then. Larvae had made simple pupal cavities without constructing a cell or reinforcing the walls. Larvae and weevils of each generation were forwarded to VVG for barcoding and further corroboration of their common identity.

Buchananius sulcatus is not commonly collected but has a wide distribution in the eastern and southeastern United States ( Kissinger 1957; O’ Brien and Wibmer 1982). It is reported here from Maryland, new state record, for the first time. The only congener in the United States is Buchananius striatus (LeConte) , whereas the genus is extremely diverse in the Neotropical Region (JP, unpublished data). The fungal host T. peltatum occurs in tropical to temperate areas of both hemispheres ( Doi 1975; Samuels and Ismaiel 2011). A possible attraction of adult B. sulcatus by mold and fungal growth was reported first by Kissinger (1957). In late May 2010, one of us (JP) observed an aggregation of the same species on a fallen, ca. 30 cm long, 5 cm thick, dead beech branch in Rock Creek Park, DC. The branch was partially covered with a firm but not completely dry crust of white fungal growth, on which the weevils fed during approximately one week of captivity. Larvae or larval work were not detected when the branch was dissected two weeks later. A series of an undescribed species of Buchananius Kissinger was taken by S. and J. Peck (Ottawa, Canada) on a fungus-infested fence pole in Cuba (Canadian Museum of Nature, label data). These observations suggest that Buchananius species may feed on or even develop in or at fungi that have less bulky stromata than T. peltatum .

Trophic interactions between weevils and fungi evolved independently and repeatedly, particularly in the Anthribidae , Brentidae , Platypodinae , and Scolytinae ( Beeson 1925; Holloway 1982; Farrell et al. 2001). The following two instances became known in the Conoderinae , purportedly a sister group of the Baridinae (Zherikhin and Gratshev 1995) . Thompson (1996) cited H. Roberts, who found larval Phaenomerus lineatus Pascoe in black-lined cells inside their host tree, indicating mycetophagy. Pakaluk and Anagnostakis (1997) reported feeding of adult Acoptus suturalis LeConte on cankers of the chestnut blight fungus, Cryphonectria parasitica (Murrill) Barr. Most known mycetophilous weevils are associated with ascomycetes, only a few with basidiomycetes ( Holloway 1982; Harrington 2005). Buchananius sulcatus is the first known case of a weevil that develops inside the stroma of a fungus. Because the larva disgorges the undigested chitinous components of the diet, it needs to stay close to the surface to discharge waste that otherwise would obstruct the gallery ahead ( Fig. 3 ).

Material Examined. Adult B. sulcatus , “A”; larvae, “L”: “ MARYLAND: A. Arundel Co., 8 km ESE Laurel ( North Tract Patuxent Res. Ref. ), 39°02′21″ N, 76°46′06″ W, 11 August 2012, Coll. W. E. Steiner / On fungus stroma Hypocrea peltata on fallen branch of beech, mixed forest” (7A); same data except “ 22 August 2012 ” (5A); same data except “ 29 August 2012 ” (1A, ∼ 30L); same data except “ 9 September 2012, Colls. W. E. Steiner & J. M. Swearingen ” (2A, 4L). Associated fungal samples, dry or in ethanol, with same locality labels and “Host fungus of weevil Buchananius sulcatus on fallen branch of beech, mixed forest”. Cox1 barcode region of six larvae and two collected and two reared adults available at dx.doi.org/10.5883/ BOLD: ACG2161 . Specimens are deposited in the Canadian National Collection of Insects , the US National Museum, and JP’ s personal collection .

Figures

Figs. 1–3. 1) Dead, fallen canopy branch of Fagus grandifolia with Trichoderma fungus growing on top; 2) Close-up of Trichoderma peltatum with discharged larval frass on surface; 3) Cross-section of stroma showing two adult Buchananius sulcatus (arrows; inset with enlarged dorsal view) and larval work. Figs. 1 and 2 taken by J. Swearingen on 9 September 2013; Fig. 3 prepared by JP.