Bombus (Thoracobombus) pensylvanicus (De Geer)

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 : 13

Bombus (Thoracobombus) pensylvanicus (De Geer)

‘American Bumble Bee’

Bombus pensylvanicus [as B. americanorum (Fabricius) ] was listed as the “most widespread and common species” in the state in Chandler & McCoy’s (1965) study. Its statewide occurrence is much reduced today, although it remains widespread ( Fig. 1). The contemporary occurrence of B. pensylvanicus (50%) is about one-third lower than its historic occurrence (82%, Fig. 3). Only a single record occurred in the period between our sampling intervals: Faulkner Co., September 6, 1976. This state-level pattern reflects what has also been observed throughout the range of B. pensylvanicus , and many sources consider B. pensylvanicus to be a declining species ( Cameron et al., 2011; Colla & Packer, 2008; Colla et al., 2012; Grixti et al., 2009). Although there are indications of a range-wide decline of B. pensylvanicus , it is likely that not all areas are reflecting the same shifts in abundance or occurrence. For example, B. pensylvanicus was abundant in the extreme south and western portions of its range (Louisiana, Oklahoma, and Texas) in recent surveys, although it was absent from much of the northern and eastern areas in which it was expected to occur ( Cameron et al., 2011). Similarly, B. pensylvanicus was absent from the northern region of Illinois in recent surveys, although it was known from northern Illinois in historical records ( Grixti et al., 2009). With contemporary records occurring throughout the state and in each ecoregion, we found no geographic pattern in the occurrences of B. pensylvanicus within Arkansas. This heterogeneity among regional studies highlights the utility of localized studies in determining the conservation status of species of interest.

GLOSSA LENGTH: Long (6.41 ± 0.58 mm).

ADULT ACTIVE PERIOD: Late season with a long active period (82 days). Majority: late June through mid-September; Earliest: May 13; Latest: October 16.

PREFERRED PLANTS: Baptisia alba (wild white indigo, Fabaceae ), Vernonia Schreb. (ironweed, Asteraceae ), T. canadense ( Canada germander, Lamiaceae ), M. fistulosa (wild bergamot, Lamiaceae ), A. esculentus (okra, Malvaceae ), Solanum carolinense Linnaeus (Carolina horsenettle, Solanaceae ), Cirsium discolor (Muhl. ex Willd.) Spreng. (field thistle, Asteraceae ), S. azurea (azure blue sage, Lamiaceae ), S. integrifolium (wholeleaf rosinweed, Asteraceae ), V. villosa (winter vetch, Fabaceae ).