Bombus (Pyrobombus) bimaculatus Cresson

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 : 10

Bombus (Pyrobombus) bimaculatus Cresson

‘Two-spotted Bumble Bee’

Bombus bimaculatus is, along with B. auricomus , one of the earliest species to become active in Arkansas. It also has the shortest active period in northwest Arkansas, with the majority of individuals spotted over a period of only 48 days. Although Chandler & McCoy (1965) stated that they observed this species in the state during late summer and early fall, only three of 214 specimens of B. bimaculatus in the UAAM collection were collected after July. These were collected in 1964 and 1976, and all were from Washington County. In spite of its short active period, the proportion of counties with records of B. bimaculatus increased dramatically from 13% of sampled counties in the historic period to 44% in the contemporary period ( Fig. 3). Bombus bimaculatus showed a strong preference for non-native vetch species, with 64% of all specimens observed on V. sativa and V. villosa . Vetches have been naturalized through much of the southeastern North America and are often grown as forage and cover crops, and for erosion control ( Owsley, 2011). Perhaps their ability to use novel plant resources has contributed to the increased presence of B. bimaculatus in Arkansas, although other studies have also reported recent increases in B. bimaculatus throughout its range ( Cameron et al., 2011; Colla & Packer, 2008; Colla et al., 2012).

GLOSSA LENGTH: Medium (5.65 ± 0.64 mm).

ADULT ACTIVE PERIOD: Early season with a short active period (48 days). Majority: mid-May through late June; Earliest: April 22; Latest: August 1.

PREFERRED PLANTS: Vicia villosa (winter vetch, Fabaceae ), V. sativa (garden vetch, Fabaceae ), P. digitalis (foxglove beardtongue, Plantaginaceae ), T. canadense ( Canada germander, Lamiaceae ).