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Bombus rubicundus Smith, 1854
Bombus napensis Spinola, 1854, nomen nudum Bombus bicolor Friese, 1903 Bombus (Rubicundobombus) rubicundus Smith, 1854 Pyrobombus (Cullumanobombus) rubicundus (Smith, 1854)

Life   Insecta   Hymenoptera   Apoidea   Apidae   Bombus
Subgenus: Cullumanobombus

Bombus rubicundus, Ruddy Bumble Bee
© Copyright John Ascher, 2006-2014 · 1
Bombus rubicundus, Ruddy Bumble Bee

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Bombus rubicundus, Ruddy Bumble Bee
© Copyright John Ascher, 2006-2014 · 1
Bombus rubicundus, Ruddy Bumble Bee
Identification
Extracted by H. E Milliron. A Monograph of the Western Hemisphere Bumblebees (Hymenoptera: Apidae; Bombinae) II. The Genus Megabombus Subgenus Megabombus. The Entomological Society of Canada, Ottawa 1970. pp. 239-330.


Description. Queen. Length, 22.0 mm; width at wing bases, 11.0 mm; abdomen, 12.0 mm, width across T2, 11.0 mm; front wing length, 18.0 mm, width, 7.0 mm. Head: Frontal outline (excluding mouthparts) roundly trapezoidal, its widest dimension about equal to the median height, the temples broadly and evenly rounded, vertex only weakly arcuate trans­ versely; vertical region weakly concave laterad of middle, for the most part densely covered with small (follicular) punctures, moderately inclined toward occiput; ocular half of ocel- locular area well covered with small punctures, the ocellar half smooth and shiny; compound eyes noticeably more broadly rounded below than above, their inner margins slightly in­ curved, about equally apart above and below; ocelli of medium size, positioned in a weak arc distinctly closer together than their diameters, the lateral ones almost touching the supra­ orbital line; interocellar and ocellocular lines about equal; malar space slightly less than distance between (and including) mandibular articulations, virtually impunctate and only very faintly concave transversely; labrum about twice as wide as thick, the ventral margin mostly arcuate, the shelf somewhat irregular and neither sharp nor prominent, the tubercles not sharp, irregularly and coarsely sculptured, flattened above, their mesal summits not separated by a sharp intertubercular depression; flagellum nearly If times longer than the scape, FI nearly as long as the combined lengths of F2 and F3, the latter nearly li times longer than quadrate F2; clypeus H times wider at the widest part near base than its median height, evenly but not strongly convex, the median area with medium punctures (most are follicular). Epipygium: Distal half bluntly conical. Legs: Mesobasitarsite 4 times longer than widest part which is nearly equal to the length of longest hairs of the posterior fringe, most of outer surface concave longitudinally, the distal angles blunt, equally extended with a shallow emargination between; hind tibia with the outer surface microscopically granulose, only weakly convex longitudinally along proximal two-thirds becoming shallowly concave distally, the widest part of the segment nearly equal to the length of longest hairs of corbicular fringe; metabasitarsite with most of outer surface only shallowly concave, the posterior margin evenly arcuate along proximal half becoming straight beyond, the widest part of segment at least about 3 times wider than the length of longest hairs of the posterior fringe, the sharper disto- posterior angle only slightly extended beyond the distoanterior one, at most only a very shallow emargination between. Pubescence: Most of medium length, fine, dense and rather uneven, that on most of the scutellum and on abdominal T4-5 being longer and looser; mesobasitarsal posterior fringe moderately dense, composed of longer mostly straight hairs along proximal half, gradually becoming short distally; corbicular fringe rather dense mostly composed of long hairs that are straight or nearly so except those at the base are short and those distally gradually become short, most there being slightly bent; metabasitarsal posterior fringe not dense, being short at the base becoming longer toward the middle and gradually becoming very short and sparser distally, most hairs being only very weakly arcuate. Color: Head pale reddish with very little black (if any); thorax and abdominal terga coppery red; legs with pale reddish pile on coxae, trochanters, and ventrally on the femora, otherwise black. Wings rather strongly and uniformly stained with brownish black.

Worker. Length, 12.0 mm; width at wing bases, 6.5 mm; abdomen, 6.0 mm, width across T2, 6.5 mm; front wing length, 12.0 mm, width, 4.0 mm. Proportionately very similar morphologically to the queen except the diagnostic features are more diminutive; the epipygium does not possess as prominent a conical elevation on its distal half. Color: Head pre­ dominantly black with some burnt sienna intermixed on the face; thorax bright coppery red; legs black with only a slight trace of burnt sienna at their bases; abdominal T1 coppery red, T2-3 black, T4 predominantly (if not entirely) coppery red, T5 predominantly black with at most only a few coppery red hairs laterally, T6 black, the abdominal venter mostly brownish black. Wings stained as those of the queen except slightly paler.

Male. Length, 12.0 mm; width at wing bases, 6.5 mm; abdomen, 6.0 mm, width across T2, 6.5 mm; front wing length, 14.0 mm, width, 4.5 mm. Head: Frontal outline (excluding mouthparts) very roundly trapezoidal, the narrow temples evenly and broadly rounded, vertex transversely flattened, the widest dimension a little greater than the median height; vertical region flat and covered with small to medium (follicular) punctures, only slightly inclined toward occiput; ocelli rather large, much closer together than their diameters, situated in nearly a straight line well below the supraorbital line; ocellocular area about as wide as the diameter of an ocellus, ocular half with some small punctures, the ocellar half smooth and nearly flat, interocellar line nearly twice as long as the ocellocular line; compound eyes somewhat swol­ len, almost equally rounded above and below, their inner margins subparallel except only weakly incurved; malar space about as long as the distance between (and including) mandibular arti­ culations, nearly smooth having a weak transverse convexity below; labrum little more than twice as wide as its median thickness, the ventral margin arcuate (except for a very weak median emargination in a certain aspect), the surface for the most part punctate, the “callosities” almost imperceptible; flagellum nearly 21 times longer than the scape, FI equally as long as F3 which is about 11 times longer than quadrate F2. Legs: Mesobasitarsite sub- rectangular, nearly 51 times longer than its widest part which is about half the length of longest hairs of the posterior fringe, the outer surface mostly flat, the distal angles both blunt the anterior one being extended considerably beyond the posterior one with only a slight emargination between; outer surface of hind tibia microscopically granulose, convex longitudinally mostly anteriad of the middle, the widest part of segment about equal to the length of longest hairs of the posterior fringe; metabasitarsite subrectangular, the outer surface nearly flat, the widest part about f- the length of longest hairs of the posterior fringe, the posterior margin strongly arcuate at the base, beyond nearly straight, the distal angles rather similar to those of the mesobasitarsite. Pubescence: Fine, rather dense and even, perceptibly longer and looser on the vertical region, posteriorly on the scutellum and on the distal abdo­ minal terga; mesobasitarsal posterior fringe for the most part long, rather dense, consisting almost entirely of straight hairs; hind tibial posterior fringe long except shorter basally and distally, rather dense, the hairs straight or nearly so except those distally are arcuate; metabasi- tarsal posterior fringe comparatively long throughout, moderately dense, at most the hairs are only very weakly arcuate. Genitalia and seventh and eighth abdominal sterna (PI. XIX). Color: Head brownish black (or black) with an intermixture of pale burnt sienna on the face; thorax bright coppery red; legs black with some burnt sienna at their bases especially on the coxae and trochanters; abdominal T1 coppery red, T2 predominantly black with a few coppery red hairs intermixed medially, T3 black, T4-5 predominantly coppery red with black at the sides, T6 mostly black with some coppery red hairs intermixed medially, T7 predominantly pale burnt sienna with only blackish hairs intermixed medially. Wings stained as those of the worker but slightly paler.

Comments. Structurally I have detected no important variability in this species. Chromatically there is a rather wide range in the amounts of coppery red and dark (brownish black) pile especially that of workers and males particularly on abdominal T2-6; the queen is usually as redescribed above, but sometimes a varying amount of intermixed dark pile might occur on T2-3 and T5, and T6 might be predominantly to entirely black.

This taxon has no close ally in the Western Hemisphere. Specimens represent­ ing definite locality records from any part of Central America have not been en­ countered in this study though I have examined one queen labeled Honduras which to me is doubtful.


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