Bombus (Bombias) auricomus (Robertson)

Tripodi, Amber D. & Szalanski, Allen L., 2015, The bumble bees (Hymenoptera: Apidae: Bombus) of Arkansas, fifty years later, Journal of Melittology 2015 (50), pp. 1-17 : 9

Bombus (Bombias) auricomus (Robertson)

‘Black & Gold Bumble Bee’

Bombus auricomus was not listed as occurring in Arkansas in Franklin’s (1912) account of the bumble bees of the New World, but was recognized as B. nevadensis auricomus in seven counties in Chandler & McCoy’s (1965) statewide account ( Fig. 1). Bombus auricomus and its close relative in the west, B. (B.) nevadensis Cresson , are currently thought of as separate species ( Cameron et al., 2007; Scholl et al., 1992). Bombus auricomus is the longest-glossa bumble bee in the state, but it is an early-season species compared to others in the area. It has a relatively short active period and is among the rarer species in the state (7% of specimens of Bombus in the UAAM collection). In northwest Arkansas, B. auricomus is one of the earliest species to establish colonies, and these colonies are typically completed by early July. In other areas of its range, B. auricomus seems to follow a different seasonal schedule. The species is a late-season species relative to other species in Ontario ( Colla & Dumesh, 2010) and a mid-season species in Alberta ( Hobbs, 1965). In Virginia, males were still actively seeking mates in mid-August ( Alcock & Alcock, 1983), suggesting that colonies in Virginia persist much later than they do in Arkansas. The distribution of B. auricomus in North America seems to be primarily north of Arkansas. Indeed, the southern half of Arkansas is not included in recent range maps of the species ( Colla et al., 2011; Williams et al., 2014), although historic records of its occurrence are known ( Fig. 1). Although uncommon throughout the state, the occurrence of B. auricomus has increased between the historic (18%) and contemporary periods (31%, Fig. 3).

Bombus auricomus has garnered some conservation attention of late. Throughout North America, B. auricomus persists in less than 50% of its historic range, but its relative abundance appears unchanged ( Colla et al., 2012). In Arkansas, the presence of B. auricomus in the extreme southwestern region of the state was not confirmed in recent surveys of the Blackland Prairie remnants, prompting some concern for its status in the region ( Warriner, 2011). In the central portion of its range in Illinois, contemporary surveys show that B. auricomus is as widely distributed and abundant today as in the past ( Grixti et al., 2009). As with species like B. fraternus and B. variabilis , the relative rarity of B. auricomus in some areas of its distribution renders collection records inconsistent and creates a challenge for comparative studies seeking to establish the conservation status of this species.

GLOSSA LENGTH: Long (7.12 ± 0.39 mm).

ADULT ACTIVE PERIOD: Early season with a short active period (58 days). Majority: mid-May through early July; Earliest: April 18; Latest: August 11.

PREFERRED PLANTS: Monarda fistulosa (wild bergamot, Lamiaceae ), Baptisia alba (white wild indigo, Fabaceae ), B. bracteata (longbract wild indigo, Fabaceae ), Penstemon digitalis Nutt. ex. Sims. (foxglove beardtongue, Plantaginaceae ), Pycnanthemum tenuifolium Schrad. (narrowleaf mountainmint, Lamiaceae ).