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Description. Queen. Length, 21.0 mm; width at wing bases, 10.0 mm; abdomen 11.0 mm, width across T2, 11.0 mm; front wing length, 18.0 mm, width, 6.5 mm. Head: Frontal outline (excluding mouthparts) trapezoidal, the median height about equal to widest dimension, temples rather sharply rounded, the vertex transversely slightly arcuate; vertical region noticeably concave and smooth diagonally above each lateral ocellus, otherwise mostly flat, rather well covered with small irregular (follicular) punctures, somewhat strongly inclined toward the occiput; most of ocellocular area with small to minute punctures, not deeply concave laterad of lateral ocellus; compound eyes little more broadly rounded below than above, their inner margins only slightly incurved, subparallel; ocelli of medium size, separated from one another by about their diameters in a nearly straight line just below the supra orbital line; interocellar and ocellocular lines about equal; malar space only slightly (if any) longer than distance between (and including) mandibular articulations, outer surface weakly concave transversely, mostly smooth, with some minute pile posteriorly; labrum about 2 times as wide as thick, its ventral margin arcuate, the tubercles flattened and not very prominent or separated by any sharp intertubercular depression, the shelf rather weak; flagellum nearly If times longer than scape, FI distinctly longer than the combined lengths of F2 and F3 the latter being distinctly longer than quadrate F2; clypeus evenly but not strongly convex, covered with well separated small shallow punctures, the widest part near base about equal to median height. Legs: Mesobasitarsite elongate-rectangular, about 4 times longer than widest part which is only slightly less than the length of longest hairs of the posterior fringe, the outer surface for the most part shallowly concave longitudinally, the sharper distoposterior angle extended slightly beyond the distoanterior one with only a weak emargination between; outer surface of hind tibia microscopically granulose with a rather and somewhat irregular longitudinal convexity just anteriad of middle, the widest part of segment about equal to the length of longest hairs of the posterior fringe; metabasitarsite subrectangular, little more than 21 times longer than widest part which is considerably wider than the length of longest hairs of the posterior fringe, the posterior margin for the most part only weakly arcuate, the outer surface broadly and shallowly concave longitudinally, the distoposterior angle acute and considerably extended beyond the right angled distoanterior one with only a slight emargination between. Pubescence: Fine, rather dense, even except somewhat longer on most of head, scutellum and most of abdomen especially distally (except segment 6); mesobasitarsal posterior fringe moderately dense, composed of mostly straight hairs, longest of which are near base of segment beyond gradually becoming shorter; hind tibial posterior fringe rather dense, long, composed mostly of straight hairs most of which along the distal half are somewhat longer than the others; metabasitarsal posterior fringe of medium density, composed of both slightly bent and straight hairs, longest on basal half of margin, beyond gradually becoming shorter distally. Color: Head, thorax, and legs black; except for a few black hairs medially on the face of abdominal XI all abdominal terga bright orange red, the pile on much of T4 and on T5-6 being somewhat paler, the abodminal venter dark (black) with some intermixture of reddish yellow on S3-4, along the distal margin of S5 and on S6. Wings lightly stained with brown.
Worker. Length, 16.0 mm; width at wing bases, 8.0 mm; abdomen, 8.0 mm, width across T2, 9.0 mm; front wing length, 12.0 mm, width, 4.5 mm. Except for difference in size, the diagnostic structural features in this caste are proportionally so similar to those of the queen that they need not be repeated here in detail. The color pattern is also like that of the queen except that usually there is proportionately less black on the face of abdominal T1 or none at all. The wings are slightly paler.
Male. Length, 17.0 mm; width at wing bases, 8.0 mm; abdomen, 9.0 mm, width across T2, 8.5 mm; front wing length, 15.0 mm, width, 5.0 mm. Head: Frontal outline (excluding mouthparts) rather roundly trapezoidal, the widest part slightly greater than the median height, the very narrow temples abruptly rounded, the vertex transversely nearly straight; vertical region mostly flat and well covered with small (follicular) punctures, moderately inclined toward the occiput; ocelli medium in size, located noticeably closer together than their diameters in a very weak arc distinctly below the supraorbital line; ocellocular area not markedly concave laterad of lateral ocellus and with only a few small punctures close to eye margin; interocellar line about twice as long as ocellocular line; compound eyes slightly swollen, somewhat more narrowly rounded below than above, their inner margins straight and subparallel; malar space about as long as distance between (and including) mandibular articula tions, outer surface transversely weakly convex, smooth; labrum little more than twice as wide as its median thickness, the ventral margin straight except rounded at the corners, transversely slightly concave, the callosities weak, punctate, well separated; clypeus evenly convex, rather densely covered with small (many follicular) punctures; flagellum little mote than 21 times longer than scape, FI considerably longer than rectangular F3 and subequal to the combined lengths of F2 and F3, the latter nearly li times longer than F2. Legs: Mesobasitarsite subrectangular, nearly 4 times longer than widest part which is little more than 1 the length of longest hairs of the posterior fringe, the outer surface longitudinally concave, the rounded distoposterior angle slightly in recess of the sharper distoanterior angle with only a weak emargination between; outer surface of hind tibia mostly microscopically granulose, longitudinally with a rather weak irregular convexity, the widest part of segment nearly equal to the length of longest hairs of the posterior fringe; metabasitarsite almost rectangular, its widest part equal to about £ the length of longest hairs of the posterior fringe, the outer surface rather flat, the distal end of segment subtruncate, the posterior margin for the most part nearly straight except arcuate at very base. Pubescence: In character very similar on the body to that of queen and worker except not as compact (looser) especially on the abdomen; mesobasitarsal posterior fringe moderately dense, composed mostly of long nearly straight hairs, those along the distal third of margin becoming gradually shorter; hind tibial posterior fringe rather dense, mostly composed of nearly straight long hairs except the distal ones which are shorter and arcuate near their tips; metabasitarsal posterior fringe moderately dense, composed of long nearly straight hairs along the proximal two-thirds of margin, gradually becoming shorter beyond. Genitalia and seventh and eighth abdominal sterna (PI. XX). Color: Exactly like that of the queen except the pile on the distal abdominal terga (T5-7) is not noticeably a paler orange red than on the preceding terga. Wings are stained about like those of the worker.
Comments. This handsome species appears to be one of the most constant regarding structure and color pattern of all bumblebees of the Western Hemisphere. If color variation does occur I was unable to detect it in the limited amount of material at hand. This high altitude species has its closest relative in P. (C.) coccineus (Fr.), which occurs at about the same altitude.
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Updated: 2024-10-31 23:06:34 gmt © Designed by The Polistes Corporation |