Reprinted with permission from: Mitchell, T.B. 1962 Bees of the Eastern United States. North Carolina Agricultural Experiment Station Technical Bulletin No. 152. |
QUEEN—Length 18-22 mm., breadth of abdomen 9-9.5 mm.; black, apical tarsal segments becoming somewhat more brownish-piceous, spurs and tegulae black to piceous; wings uniformly but rather lightly infuscated, veins testaceous to black; pubescence rather short but dense, largely pale on head, quite copious above clypeus and around antennae where it is nearly white, with a few dark hairs at each extreme side, pale yellow on vertex and occiput, with a few black hairs laterally, largely fuscous on cheeks, becoming elongate below; pubescence bright yellow on pronotum, tubercles, anterior margin of scutum, entire scutellum, and abdominal terga 1-4, black on propodeum, legs, posterior two- thirds of scutum and terga 5 and 6, that on pleura becoming somewhat more brownish-fuscous anteriorly and below; hind basitarsus and the more apical segments of the other legs with very fine, appressed, pale tomentum which does not quite obscure the surface; corbicular fringe of black, elongate hairs; lateral and upper margins of clypeus quite closely and finely punctate; the broad median area largely shining and impunctate; labrum shining, broadly truncate, with a low basal ridge on each side, broadly concave medially, with scattered, very minute punctures; apical margin of mandible with a pair of low teeth toward the upper angle, otherwise broadly rounded, outer face rather smooth, shining, punctures exceedingly minute, hardly evident; malar space smooth and shining, somewhat longer than basal width of mandibles, punctures exceedingly minute and hardly evident; length of eye about three and a half times that of malar space; punctures of face medially very fine and close, but distinct, becoming somewhat more sparse toward ocelli, space between lateral ocelli and eyes shining and largely impunctate; vertex finely and densely
punctate medially, becoming somewhat more distinctly punctate laterally but still close; lateral ocelli slightly nearer eyes than to each other, and slightly nearer each other than to margin of vertex; antennal scape somewhat more than half the total length of flagellum, basal segment of flagellum considerably longer than segment 3 which is slightly longer than 2; posterior margin of hind basitarsus very slightly curved, apex very slightly narrower than median area; tergum 6 narrowly rounded apically, surface obscurely roughened, without distinct punctures.
WORKER—Length 13 mm., breadth of abdomen 6.5 mm.; resembles queen except in size.
MALE—Length 14-17 mm., breadth of abdomen 6.5-7 mm.; black, legs somewhat reddened apically, apical tarsal segments more brownish-piceous; tegulae, and mid and hind spurs, brownish-piceous; wings uniformly but rather lightly infuscated, veins testaceous to piceous; pubescence in general quite long and copious, largely black around antennae and on face below, but with some shorter, greyish, densely plumose hairs beneath; vertex medially and occiput with elongate yellow hairs, erect and black on vertex laterally, and largely blackish or fuscous on cheeks, becoming very long beneath; pubescence yellow on pronotum, tubercles, anterior margin of scutum, entire scutellum and abdominal terga 1-4, largely black on posterior two-thirds of scutum, pleura, propodeum and legs, but pleura with intermixed pale hairs anteriorly and below, and coxae, trochanters and femora with considerable pale pubescence; abdominal terga 5 and 6 black pubescent toward base but with considerable yellow apically, tergum 7 with rather elongate black pubescence; clypeus very finely and rather closely punctate in general, median apical area becoming shining, with very minute, hardly evident punctures; Iabrum smooth and shining, apical margins slightly incurved over the median area, with a few scattered, irregular punctures medially, lateral areas impunctate and somewhat convex, median line slightly impressed; mandibles quite slender, distinctly bidentate apically, outer surface densely yellowish tomentose, fringed on lower margin with rather elongate, fuscous hairs; malar space smooth and shining, without distinct punctures, much longer than basal width of mandible, and about one- third that of eye; face very finely and closely punctate medially beneath the rather dense pubescence, becoming somewhat more coarse and sparse toward ocelli, space between ocelli and eyes shining and with only scattered, obscure punctures; vertex finely and closely punctate medially, becoming somewhat smoother and more minutely punctate laterally; basal segment of flagellum slightly longer than segment 2, somewhat shorter than 3; hind tibiae somewhat flattened, shining and sparsely punctate on outer surface, the hairs very short and entirely black; apical width of hind basitarsus very slightly less than median width; genital armature as shown (fig. 130).
DISTRIBUTION—Southern Canada and the adjacent areas of the United States, May to September.
FLOWER RECORDS — Brittain and Newton (1933) record borealis on Pyrus malus.
Often confused with B.fervidus. Told apart primarily by the hair on the face. B. fervidus males and females have entirely black hairs and B. borealis have substantial amounts of yellow hair, usually the hairs above the ocelli are entirely yellow. Note that B.fervidus can have substanitial amount of short plumose yellow hairs intermixed with the longer black hairs above the antennae.
Hair on mesepisturnum almost entirely black in B. borealis while B. fervidus has substantial yellow dorsally, but be aware that black hairs extend at least half way up in most individuals.
Extracted from: Milliron H.E., (1973). A Monograph of the Western Hemisphere Bumblebees (Hymenoptera: Apidae; Bombinae). The Entomological Society of Canada, No. 89.
Description. Queen. Length, 21.0 mm; width at wing bases, 8.5 mm; abdomen, 12.0 mm; width across T2, 9.5 mm; front wing length, 17.0 mm, width, 6.0. mm. Head: Frontal outline (excluding mouthparts) trapezoidal, about as wide as high, the temporal angles evenly arcuate; vertical region weakly convex except about ocelli, rather weakly coriaceously irregularly sculptured on ocular half of ocellocular area, the ocellar one-half smooth and polished; ocelli in weak arc, the margins of lateral ones nearly touching supraorbital line; outline of compound eye little less than 2i times higher than wide, only slightly more broadly and more evenly rounded below than above, the outer limits moderately arcuate, the inner margin almost straight; clypeus about li times wider than high, irregularly convex, most of entire anterior surface impunctate, smooth, and polished; labrum nearly twice as wide as thick, its crescent-shaped moderately punctate flattened tubercles mesially as far apart as length of FI, covered with rather stiff pubescence of irregular length; flagellum slightly less than twice as long as scape, FI equal to F2-3 combined. Legs: Mesobasitarsite elongate rectangular, its outer surface nearly flat, its distoposterior angle sharp, extended beyond the acutely rounded distoanterior angle; meta- basitarsite little more than twice as long as wide, its posterior margin only weakly arcuate basally, beyond nearly straight, the outer surface flat except inclined along posterior margin, its subacute distoposterior angle considerably extended beyond the round obtuse distoanterior angle, the posterior fringe moderately long and arcuate on proximal half, progressively shorter to absent distally. Pubescence: Dense, moderately even throughout except longer and irregular in length on face, vertex, scutellum, on abdomen laterally, and over T5 especially. Color: Face and occiput predominantly pallid yellow; thoracic dorsum and arcuate area on meso- pleuron anteriad of tegulae golden-yellow except rather indefinite median black interalar band of medium width, more broad medially, most of meso- and metapleuron black; legs black, tarsi with ferruginous tinge; abdominal Tl-4 golden-yellow, T5 black though paler distally, T6 black except dense distal paler pile. Wings moderately infumated with sombre brown through out.
Worker. Similar to the queen except smaller body dimensions (length, 14.5 mm; width at wing bases, 5.5 mm; abdomen, 6.5 mm; width across abdominal T2, 7.5 mm; front wing length, 12.5 mm, width, 4.5 mm).
Male. Length, 17.0 mm; abdomen, 9.5 mm, width across T2, 6.0 mm; width at wing bases, 6.5 mm; front wing length, 13.0 mm, width, 4.5 mm. Head: Frontal outline (excluding mouthparts) trapezoidal, slightly wider than high; compound eye about 2£ times higher than wide, broadly rounded below, more narrowly rounded above, the inner margin dorsally only weakly concave inwardly; vertex nearly flat to weakly concave posteriorly, with well separated large shallow punctures; ocular half of ocellocular area irregularly sculptured, the ocellar half nearly smooth; ocelli in nearly a straight line, situated slightly below supraorbital line, distinctly closer to one another than widest dimension of each; malar space nearly If times longer than distance between (and including) mandibular articulations, only weakly convex, microscopically granulose and bearing sparse diminutive hairs; labrum little more than twice as wide as thick, its ventral margin broadly rounded laterally and weakly emarginate medially, with long to short denser pubescence, the oval weak callosities mostly smooth and polished, between irrgularly coarsely sculptured; flagellum 4 times longer than scape, FI If times longer than F2 and slightly shorter than F3. Legs: Mesobasitarsite subrectangular, 4 times longer than greatest width, out wardly covered with short moderately dense pubescence, its outer surface weakly convex mid- Iongitudinally, the subtruncately rounded distoposterior angles about equal; metabasitarsite near ly 3i times longer than greatest width, the subtruncately rounded distoanterior angle slightly in recess of the acute distoposterior angle, the outer surface shallowly concave longitudinally, coriaceous with microscopic pubescence, the posterior margin nearly straight except weakly arcuate basally, the sparse posterior fringe short. Pubescence: Medium length, even, rather compact throughout. Genitalia, seventh and eighth abdominal sterna (PI. X II). Color: Vertical region of head, thoracic dorsum anteriad of tegulae, scutellum, abdominal Tl-4 golden-yellow; face intermixed with longer black and dense whitish; lower pleura and abdominal T5 (distally and lateroventrally) with sienneous pubescence; otherwise head and body black; legs proper mostly black with some sienneous pubescence, that on tarsi largely ferruginous to stramineous. Wings somewhat more lightly infumated than those of female.
Comments. I detect no problematic morphological variability in this taxon except that often the female clypeus is punctate to polished over all its surface even so weakly punctured midventrally. Queens at hand range in length from 23.0 to 18.0 mm; worker, 15.0 to 13.0 mm or less, as encountered in subsequent deter
minations; male, 17.5 to 14.5 mm.
This species is very closely allied to appositus (Cr.) and to the Eurasian distinguendus Mor. Senile specimens of this taxon are often mistaken for appositus. Interbreeding between borealis and appositus undoubtedly occurs in the allopatric range; many specimens seen from the western North American allopatric areas in dicate that this hybridization does actually occur.
Updated: 2019-01-16 10:13:32 gmt