Information Extracted from: Yanega, D. 2013. The status of Cockerell’s Bumblebee, Bombus (Pyrobombus) cockerelli Franklin, 1913 (Hymenoptera: Apidae). Southwestern Entomologist 38(3): 517-522.
As can be seen from the preceding listing of specimen identification labels, the taxonomic status of the bee has been a source of confusion. Franklin (1913) stated that B. cockerelli was “very closely allied to B. vagans and thorough collecting may prove that it should be considered as only a subspecies.” Based on labels the determiners attached to the existing specimens during the intervening years, at least one researcher (R. B. Miller) considered it to be a subspecies of B. vagans, while H. E. Milliron seemed to affiliate it with B. flavifrons -- an opinion evidently shared by others, as evidenced by the entry on the ITIS website, which is annotated “probable synonym of B. flavifrons (Paul Williams, pers. comm. Oct. 2006)” (ITIS 2013), though that same author now considers it to be a probable synonym of B. vagans (Williams, 2013). Structurally, B. cockerelli is extremely similar to B. vagans, with very slightly denser punctuation on the clypeus and ocellar areas, but little else readily noticed, and the coloration (anterior and posterior notum are yellow, abdominal terga 1, 2, and 5 are opaque light yellow while 3, 4, and 6 are all black except for traces of yellow at the extreme lateral edges) is remarkably similar to the Newfoundland subspecies of B. vagans (originally described as Bombus bolsteri by Franklin 1913), with the exception of numerous black hairs intermixed anteriorly on the notum, which makes the overall coloration most like the Appalachian Bombus sandersoni Franklin. However, comparisons of COI sequences of B. vagans and B. cockerelli (D. Hawks and C. Sheffield, unpublished) reveal they are at least as distinct as other species pairs within Pyrobombus, and other gene sequences place B. cockerelli near but distinct from B. vagans, as well (S. Cameron personal communication 2013). These two taxa are certainly geographically isolated to a degree that would prevent gene flow; there are no confirmed records of B. vagans from any of the states adjacent to New Mexico (Arizona, Colorado, Oklahoma, Texas, or Utah), meaning an estimated minimum distance of more than 805 km between any habitat that might reasonably be expected to harbor B. cockerelli, relative to the nearest B. vagans populations.
Combined with the known prior collecting localities, all 34 known extant specimens of B. cockerelli (21 queens and 13 workers) were found within a rectangle less than 16 km east to west, and almost exactly 48 km north to south, for approximately 800 square kilometers, smaller than the known range of any other Bombus species in the world (Garvey 2011), and none of the specimens was collected below 6,500 feet in elevation. This region encompasses the transition zone between the Sierra Blanca range (White Mountains) to the north and Sacramento Mountains to the south; even if all areas above 6,000 feet within these combined mountain ranges are considered as potential habitat for the bee, this still comprises an area no bigger than 129 by 64 km. The listing in the catalog by Krombein et al. (1979) indicating that the species occurred in Utah was based on an unpublished misidentification of a series of male specimens in the collection at Utah State University (T. Griswold personal communication), and there are no confirmed specimens from Utah or any other localities outside these mountains. The range of B. cockerelli at least partially overlaps that of the federally threatened Sacramento Mountains thistle, Cirsium vinaceum Woot. & Standl., endemic to the area near Cloudcroft; considering that the queens, at least, will visit invasive thistle, one might expect they will pollinate the endemic native thistle, as well. It is also noteworthy that few worker specimens have been seen (all from late June through mid-July), and no males. This not only suggests a very short, and late, active season (with accordingly small colony sizes), but raises the possibility that foraging workers (and males) may remain in the forest and not frequent open grassy meadows where collectors typically encounter montane Bombus. Hopefully, the confirmation of the validity and existence of this rare species will lead to investigations into its phenology, distribution, and life history.
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