Bombus (Thoracobombus) fervidus (Fabricius)

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 : 10-11

Bombus (Thoracobombus) fervidus (Fabricius)

‘Yellow Bumble Bee’

Franklin (1912) reported B. fervidus as absent throughout “the greater part of Arkansas ”, but, lacking deposited specimens, its presence could not be confirmed by Chandler & McCoy (1965). Although B. fervidus has intermittently been reported in the state ( Franklin, 1912; Warriner, 2011), and niche modeling suggests that the northwestern portion of the state could be marginally suitable for the species ( Williams et al., 2014), its presence here is dubious. A recent survey of Bombus in remnant grasslands throughout the state reported B. fervidus in Boone and Franklin Counties in 2003 ( Warriner, 2011), the first such sightings since it was reported 90 years prior ( Franklin, 1912). The Boone County specimen was the only state record of this species with a deposited voucher specimen. Another historical specimen identified as B. fervidus is among the specimens in the UAAM collection: a male collected October 1, 1963 in Columbia County in the southern extreme of the state. These two specimens deposited in the UAAM collection as B. fervidus were both males, yet investigations of genitalic characters by the authors revealed that they are actually B. pensylvanicus .

Males of B. fervidus superficially resemble some of the variants of male B. pensylvanicus , and the two species can be difficult to distinguish ( Mitchell, 1962). Although Mitchell (1962) suggests a number of external characters that can be helpful, B. pensylvanicus and B. fervidus males can only be reliably distinguished by comparing their genitalia. The most obvious difference is in the penis valves (sensu Michener, 2007; Mitchell, 1962). The enlarged apices of the penis valves of B. pensylvanicus are long and slender, while the apices of those of B. fervidus are more truncate, with the breadth and width about equal. Additionally, the interior process of the gonostylus of B. pensylvanicus is flattened and broad, unlike that of B. fervidus . Bombus fervidus was not observed in 2011–2013 standardized surveys that we conducted throughout the northwestern portion of Arkansas, despite intensive sampling each season (number of observations = 1693). The North American distribution of B. fervidus appears to be primarily western and northeastern ( Koch et al., 2012; Williams et al., 2014). To date, there are no deposited specimens of B. fervidus collected in Arkansas. Although we cannot discount its occasional presence in Arkansas, it seems more likely that records of this species in Arkansas are based on misidentifications of males, rather than true occurrences. The Arkansas Natural Heritage Commission lists B. fervidus as a species of concern within the state, with a ranking of S1, an “extremely rare” species at risk of statewide extirpation, known from Boone and Franklin Counties ( ARNC, 2014). Investing in the conservation of species that are not true residents of an area, such as vagrants or marginal species (i.e., ones that occasionally occur in an area at the extreme of the species’ range margin) is an inefficient approach to conservation that squanders scarce resources ( Rodrigues & Gaston, 2002). Because there are no vouchered specimens of this species collected in Arkansas, we recommend that this state ranking be re-assessed.

GLOSSA LENGTH: Long (6.50 ± 0.74 mm).

ADULT ACTIVE PERIOD: Not in the state.

PREFERRED PLANTS: Unknown.