Stephanopachys conicola, FISHER

Tonkel, Kirk C., Rector, Brian G., Longland, William S., Dimitri, Lindsay A. & Ivie, Michael A., 2014, Stephanopachys conicolaFisher (Coleoptera: Bostrichidae) Feeding on Decaying Western Juniper (Juniperus occidentalisHooker) Berries: A Novel Association for Bostrichidae, The Coleopterists Bulletin 68 (3), pp. 403-406 : 403-405

STEPHANOPACHYS CONICOLA FISHER ( COLEOPTERA : BOSTRICHIDAE ) FEEDING ON DECAYING WESTERN JUNIPER ( JUNIPERUS OCCIDENTALIS HOOKER ) BERRIES: A NOVEL ASSOCIATION FOR BOSTRICHIDAE

KIRK C. TONKEL, BRIAN G. RECTOR, WILLIAM S. LONGLAND Great Basin Rangelands Research Unit USDA – Agricultural Research Service Reno, NV 89512, U.S.A. [e-mail]

LINDSAY A. DIMITRI Department of Biology University of Nevada – Reno Reno, NV 89512, U.S.A. [e-mail]

AND

MICHAEL A. IVIE Montana Entomology Collection 1911 West Lincoln Street Montana State University Bozeman, MT 59717 , U.S.A. [e-mail]

The surprise discovery of a rarely collected bostrichid living in juniper berries raises issues of bostrichid evolution, stored product pest pathways, and the ecology of juniper systems. As part of a study of Juniperus occidentalis Hooker (Cupressaceae) , specimens of Stephanopachys conicola Fisher were reared from berries collected on the ground in California’ s Modoc County. Some implications of this discovery, as related to the above issues, are considered in the following discussion.

The Bostrichidae are a specialized group whose larvae scavenge starch in relatively dry, dead wood (Beeson and Bhatia 1937; Gerberg 1957; Ivie 2002). Their ability to live inside hard, low-moisture, starchrich substances, coupled with a dual aggregation pheromone system produced by males when they find starch ( Edde 2012), has preadapted them to moving into human stores of lumber, basketry, carvings, and stored foodstuffs ( Linsley 1944). This move has occurred repeatedly, starting at least in ancient Greek and Pharaonic times ( Buckland 1981; Panagiotakopulu and Buckland 1991; Elias 2010). One constraint limiting bostrichids in the move from wood-boring to stored-food systems is that the larvae are obligate internal feeders; thus, the species must be small enough for the larvae to develop completely while inside the individual grain or root, and the foodstuff must be solid enough to contain the larva and pupa. Larvae cannot survive in an exposed condition.

The subfamily Dinoderinae consists of five to seven genera (see Borowski and Wiegrzynowicz 2011; Liu and Beaver 2013), four of which are established in North America: Stephanopachys Waterhouse ; Dinoderus Stephens ; Prostephanus Lesne ; and Rhyzopertha Stephens. The original habitat of all these groups is starch-rich wood: that of Pinophyta ( Pinaceae and Cupressaceae ) in the case of Stephanopachys ; of monocots (bamboos) in the case of Dinoderus ; and of various hardwoods for the others. All but Stephanopachys have members that have invaded stored food systems, albeit with broad feeding preferences ( Fisher 1950; Ivie 2002). The species of Rhyzopertha and Dinoderus involved in stored products are not native to the New World, having been introduced via the agency of humans. Rhyzopertha dominica (F.) is an important pest of stored grain and has been recorded from the fruits, seeds, roots, twigs, or bark of 31 different plant families ( Edde 2012). Prostephanus has several species that feed on wood, with Prostephanus truncatus (Horn) recently (in evolutionary terms) invading stored grains and starchy tubers, especially on-cob maize (Nansen and Meikle 2002). The bamboo powderpost beetles of Dinoderus include four species that have moved into human stored foods with high starch content, mostly roots and tubers ( Schäfer et al. 2000).

Stephanopachys has been considered unlikely to produce a stored product pest because of the limited use of gymnosperm products as foodstuffs. Two such food items of trade value include edible pine nuts and juniper berries, the latter used primarily in the manufacture of gin but also as a spice, an herbal dietary supplement, and potpourri ingredient. The juniper berry is in actuality a female cone with fused scales. Ripe berries on trees of J. occidentalis are high in carbohydrate content, recorded as near 50% of dry weight— mainly sugars (Poddar and Lederer 1982). This finding suggests that much of the sugar in juniper berries is converted to starch after they drop from the tree and desiccate, based on the typically starchy diet of bostrichids, although there is no empirical data to support this hypothesis at present. The discovery of a Stephanopachys infesting juniper berries from the ground is surprising and yet, in hindsight, conforms to the pattern seen throughout the Dinoderinae .

The nine members of the genus Stephanopachys known to occur in North America all attack conifers ( Fisher 1950). Stephanopachys conicola Fisher ( Fig. 1 ) is perhaps the rarest of these species and was the last to be described ( Fisher 1950). It was described from one specimen (holotype) found “on” a white fir, Abies concolor (Gordon and Glendhill) Lindley ex Hillebrand (Pinaceae) , at Williams, in central Arizona, and six individuals (paratypes) “from” cones of singleleaf pinyon, Pinus monophylla Torrey and Fremont (Pinaceae) , by J. E. Patterson in the San Gabriel Mountains of southern California ( Fisher 1950). However, examination of these six paratypes in the National Museum of Natural History, Washington, DC by MAI revealed that those individuals were actually collected at Baldwin Lake, San Bernardino National Forest, California, by J. E. Patterson and S. T. Carlson. These paratypes would be six of the 13 adults reported by Keen (1958), erroneously as Stephanopachys sobrinus Casey , that were “collected and reared from beetle-killed cones of singleleaf pinyon” collected on 28 March 1938 with scattered emergence occurring until 20 June 1938. The other seven specimens are housed in the Western Forest Insect Collection, now incorporated into the Oregon State University Arthropod Collection, Corvallis, OR. Those specimens bear a determination label without a date by W. S. Fisher as Stephanopachys sobrinus (Casey) (?). It was assumed that larvae were feeding on dry cone tissues. Other than the specimens reported herein, in the course of identifying thousands of bostrichids from various museums and projects over the last 30 years, MAI has seen only one specimen beyond the type series. That specimen is from “West Utah Lake, Utah Co, Utah,” collected 27 December 1971 by D. K. Johnson using a Berlese funnel (specimen in the Montana Entomology Collection (MTEC)). This locality is probably on or near Lake Mountain, west of Utah Lake.

No known collections of S. conicola report J. occidentalis berries as a host, but all known locations of collection are inhabited by various species of juniper. Rocky Mountain juniper, Juniperus scopulorum Sarg. , is common on Lake Mountain, Utah ( Bullock 1951). The San Bernardino Mountains are home to Sierra juniper, Juniperus occidentalis var. australis (Vasek) A. Holmgren and N. Holmgren , and California juniper, Juniperus californica Carrière ( Mohlenbrock 2006) . Pinyon pine, Pinus edulis Engelm. , Utah juniper, Juniperus osteosperma (Torr.) Little , oneseed juniper, Juniperus monosperma (Engelm.) Sarg., and Rocky Mountain juniper are found in woodlands of the Kaibab National Forest in central Arizona near Williams ( Mohlenbrock 2006).

As part of a study of J. occidentalis seed ecology, berries and litter were collected from three sites in northeastern California (Madeline, Shinn Peak, and Likely; all in Modoc Co., CA) in 2011 and 2012. Collection sites were in sagesteppe habitat dominated by J. occidentalis and Wyoming big sagebrush, Artemisia tridentata ssp. wyomingensis Beetle and Young (Asteraceae) , along with varying amounts of native perennial grasses, invasive annual grasses, and forbs. Litter, including fallen berries, was collected from beneath individual J. occidentalis trees at the Likely site (41.23185°, -120.42523° elevation 1,267 m) on 4 February 2011 into separate 3.8-L (one-gallon) Ziplock® bags. Berries were isolated from litter by hand and transferred to paperboard rearing chambers (28 × 23 × 10.5 cm) with a cylindrical 12-dram, clear plastic vial inserted into the side of the box to collect emerging adult insects. Four hundred forty berries from the litter beneath one tree were moved to the chamber on 9 February 2011 and maintained at room temperature from February 2011 to January 2014.

Only the sample from Likely produced S. conicola . Sixty adult S. conicola were reared from the collection chamber. Only five of these adults migrated to the collection vial, with all others dying as adults within the rearing box. Feeding by developing S. conicola resulted in consumption of the resinous husk (or “fruit”) and the seed, leaving partially consumed, frass-filled skins of the consumed berries ( Fig. 2 ). Six additional rearing chambers with berries from the Likely site and the two other sites 20 km (Madeline site) and 60 km (Shinn Peak site) south of Likely produced no adult S. conicola . Rearing boxes containing only litter (i.e., without berries) from the three sites produced no S. conicola . Given that no other rearing boxes containing berries from the Likely site yielded adult beetles, and live adults were found one-and-a-half years after collection, these 60 adults may represent multiple generations. This suggests that the potential exists for this insect to act as a pest of stored juniper berries destined for various culinary purposes, in addition to being a novel association for this insect.

Parasitoids emerging from the rearing chamber containing berries infested by S. conicola included: one Goniozus sp. ( Hymenoptera : Bethylidae ), which emerged 15 February 2011; one unidentified pteromalid ( Hymenoptera : Pteromalidae ) that emerged 24 February 2011; and one Euderus sp. ( Hymenoptera : Eulophidae ), which emerged 1 March 2011. These parasitoids have also been reared from berries collected at other sites, and possibly attacked other insect species inhabiting these berries, although no additional potential host insect species emerged from the rearing chamber.

Voucher specimens of the bostrichids are deposited at the Montana State University Montana Entomology Collection (MTEC), Bozeman, MT; the USDA-ARS Great Basin Rangelands Research Unit, Reno, NV; KCT personal collection; and the Nevada State Dept. of Agriculture. Parasitoid vouchers are deposited in the USDA-ARS Great Basin Rangelands Research Unit, Reno, NV.

Figures

Fig. 1. Stephanopachys conicola, lateral and dorsal views.

Fig. 2. Juniperus occidentalis berries damaged (left) by Stephanopachys conicola and undamaged (right).