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Bombus brachycephalus Handlirsch, 1888
Bremus neotropicus Frison, 1928; Bombus krusemani Asperen de Boer, 1990; Pyrobombus (Cullumanobombus) brachycephalus (Handlirsch, 1888)

Life   Insecta   Hymenoptera   Apoidea   Apidae   Bombus
Subgenus: Cullumanobombus


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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, 19.0 mm; width at wing bases, 10.0 mm; abdomen, 10.0 mm, width across T2, 11.0 mm; front wing length, 18.0 mm, width, 7.0 mm. Head: Frontal outline (excluding mouthparts) rather roundly trapezoidal, the median height nearly equal to the widest part, somewhat sharply rounded at the temples, the vertex nearly straight across; vertical region only weakly concave to almost flat and noticeably inclined toward the occiput, mostly well covered with small to medium irregular closely set (follicular) punctures; ocular half of ocellocular area weakly inconspicuously punctate, the ocellar half largely smooth; compound eyes little more broadly rounded below than above, their inner margins sub­ parallel except convergent above; ocelli rather large, situated in a weak arc much below the supraorbital line and noticeably closer together than their diameters; interocellar line about l i times greater than the ocellocular line; malar space a little less in length to distance between (and including) mandibular articulations, its outer surface only weakly irregularly convex and inconspicuously sculptured; labrum about 21 times wider than its greatest thickness, the ventral margin arcuate, the shelf weak, the tubercles rather coarsely punctate for the most part and flat ventrally, their mesal summits subconical and well separated by a rather deep intertubercular depression that is not as wide as the length of FI; flagellum nearly twice as long as the scape, FI about equal to the combined lengths of F2 and F3, the latter noticeably longer than subrectangular F2 which is only a little longer than wide; clypeus rather evenly but not strongly convex, its median height about equal to the widest portion near base, bearing above not dense but rather irregular large and medium punctures, less punctate below. Legs: Mesobasitarsite elongate-rectangular, about 4 times longer than its widest part which is nearly equal to the length of longest hairs of the posterior fringe, the outer surface broadly and shallowly concave longitudinally, the sharper distoposterior angle extended somewhat beyond the blunter distoanterior one with a distinct emargination between; widest part of hind tibia nearly equal to the length of longest hairs of the posterior fringe, the outer surface granulose, for the most part nearly flat with a slight longitudinal convexity just inside the anterior margin; metabasitarsite subrectangular, about 2-f times longer than its widest part, which is about twice as wide as length of longest hairs of posterior fringe, the posterior margin rather evenly but not strongly arched from base to distal end, most of the outer surface weakly and broadly concave longitudinally to nearly flat, the sharper distoposterior angle extended somewhat beyond the blunter distoanterior one with only a shallow emargination between. Pubescence: Rather short, fine and moderately dense, a little longer on the scutellum and on most of the abdomen; mesobasitarsal posterior fringe moderately dense, composed mostly of straight (or nearly so) hairs that are longest along the basal third of margin becoming gradually very short at the distal end; hind tibial posterior fringe moderately long and dense, composed mostly of weakly bent to nearly straight hairs that are shortest proximally, longest medially and shorter distally; metabasitarsal posterior fringe not dense, composed mostly of straight rather short hairs that are longest medially becoming very short beyond. Color: Head, thorax, legs, and abdominal Tl-3 black, T4-6 light ferruginous; venter black except pile distally on abdominal S4-5 and all that on S6 pale ferruginous. Wings uniformly black with some violaceous reflection under certain lights.

Worker. Length, 12.5 mm; width at wing bases, 7.0 mm; abdomen, 6.5 mm, width across T2, 7.0 mm; front wing length, 13.0 mm, width, 4.5 mm. Except for the smaller body size and more diminutive comparative relationships there seems to be little (if anything) of importance in this caste that is different from that detailed for the queen.

Male. Length, 13.5 mm; width at wing bases, 7.5 mm; abdomen, 6.5 mm, width across T2, 7.0 mm; front wing length, 13.0 mm, width, 4.5 mm. Head: Frontal outline (excluding mouthparts) roundly trapezoidal, its widest part a little more than the median height, broadly rounded at the temples, vertex transversely very weakly arcuate to nearly straight; vertical region nearly flat, mostly well covered with small to medium (follicular) punctures, only slightly inclined toward the occiput; ocelli comparatively large, situated in an arc much below the supraorbital line, removed from one another by a distance much less than their diameters; ocellocular area distinctly narrower than the diameter of a lateral ocellus, without any strong punctures and weakly ridged adjacent to compound eye; interocellar line fully twice that of the ocellocular line; compound eyes somewhat swollen, nearly equally rounded above and below, their inner margins nearly straight and only slightly converging above; malar space about equal to the distance between (and including) mandibular articulations, the outer surface irregularly weakly convex and with very few small punctures; clypeus rather evenly convex, without very dense pile but well covered with numerous small (follicular) punctures except for a small median circular area below; labrum about twice as wide as thick, its ventral margin nearly straight except arcuate at the ventrolateral corners, the callosities very weak and not sharply separated, with few punctures; flagellum nearly 3 times as long as scape, FI little longer than F3 which is about li times longer than F2, the basal flagellar segments weakly crenulate above. Legs: Mesobasitarsite elongate-rectangular, nearly 4 times longer than its widest part which is about f as wide as the length of longest hairs of the posterior fringe, the outer surface very shallowly concave longitudinally, the distal end subtruncate with the distal angles about equally extended, the posterior one sharper; metaba­ sitarsite little more than 3 times longer than widest part which is about i as wide as longest hairs of the posterior fringe, the outer surface nearly flat, the subtruncate distal end only a little wider than the base with the sharper distoposterior angle extended only slightly beyond the distoanterior one, the posterior margin of segment evenly arcuate from base to near distal end. Pubescence: Short, fine and rather dense, somewhat longer on the vertical region, posteriorly on the scutellum and on most of the abdomen; mesobasitarsal posterior fringe composed mostly of nearly straight not dense and rather long hairs except at base and distal one-third of margin; most of outer surface of hind tibia moderately well covered with short fine hairs that are somewhat stouter adjacent to the anterior margin; metabasitarsal posterior fringe not dense and composed of straight to weakly bent rather long hairs, those at the base and distal end of margin being shorter. Genitalia and seventh and eighth abdominal sterna (PI. XVI). Color: Head black to brownish black except for some fine pale pile on the face above the clypeus; thoracic dorsum mostly brownish black with largely dull or tawny yellow on the anterior portion of the mesoscutum and very little of this color posteriorly on the scutellum, the thoracic mesopleuron tawny yellow to leg bases, the metapleuron brownish black; legs black to brownish black; abdominal T1 with brownish black on its anterior face but distally and distolaterally tawny yellow, T2 mostly tawny yellow with few intermixed dark hairs in the middle, T3 black across most of the base but distally and laterally tawny yellow, T4-5 black medially and mostly tawny yellow laterally, T6-7 mostly tawny yellow; venter largely brownish black except for some tawny yellow distolaterally on most of the abdominal sterna. Wing deeply infumated but considerably paler than those of the female.

Comments. I have not detected any troublesome structural variation in this taxon and the color pattern of the females is quite constant, closely resembling that of Megabombus (M.) diligens (Sm.). However, the males are very variable chro­ matically on both the thorax and abdomen; the one used for the redescription is about halfway between the extremes. Prison (1928*7: 151-152, fig. 150!), who described this species as new under the specific name neotropicus, possessed only two variable males; his holotype has the pronotum, scutellum, and thoracic pleuron pale yellowish whereas the paratype has the scutellum and thoracic pleuron dark or chocolate brown. From his description abdominal T1 is all pale yellowish while that of the paratype is dark or chocolate brown; another color difference between the Prison holotype and the specimen described refers to abdominal T6-7 which are in his case pale yellowish laterally and the remainder of each dark or chocolate brown. All these chromatic conditions, and some additional ones and all their intergrades, have been examined.


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FamilyScientific name @ source (records)
Fabaceae  Crotalaria @ EMEC (1)

Dalea @ EMEC (1)
Lamiaceae  Leonotis nepetifolia @ LACM_ENTB (2)

Salvia @ EMEC (2)

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Updated: 2024-03-29 07:18:08 gmt
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