Extracted from Bumble Bees and Cuckoo Bumble Bees of California by Thorp, R. (1983). |
Bombus morrisoni Cresson, 1878, Proc. Acad. NaL Sci. Phila., p. 183. q, w, nf. Lectotype q, Colorado (#2632 ANSP) (selected by Cresson, 1916).
Geographic range (Map 3). W of 100° longitude, western South Dakota S to New Mexico and W to southern British Columbia, Canada, and S to Sonora, Mexico.
California records. ALPINE Ca: Carson Pass; Leviathan Peak, 2710 m; Woodfords. INYO Ca: Alabama Hills; Big Pine, and 5 km E and 6.5 km S; Bishop, 16 km N; Deep Spring Lake; Independence; Lone Pine; Mazourka Canyon; Oak Creek; Onion Valley, Inyo NatL For.; Panamint Mtns.; Silver Canyon, White Mtns.; Surprise Canyon; Westgard Pass; Whitney Portal;
BUMBLE BEES AND CUCKOO BUMBLE BEES OF CALIFORNIA 21
Wyman Canyon, White Mtns. LASSEN CO.: Honey Lake, Janes-vilte; Slandish, 6.5 km W. MODOC CO.: Cedar Pass; Jumper Flat; Lake City, Newell; Saddleblanket Flat. MONO CO.: Benton; Bridgeport; Convict Lake; Crestview, 13 km S; Crooked Creek, While Mtns.; Crowley Lake; Grant Lake; Mill Creek; Monitor Pass; Mono Lake, 16 km N Lee Vining; Pickel Meadows; Rock Creek; Tom's Place; Topaz Lake. NEVADA CO.: Truckee. PLUŽMAS Co.: Blairsden; Keddie, 3 km W. SHASTA CO.: Hat Creek P.O. SIERRA Co.: Sierraville. SISKIYOU CO.: Montague; Scott Bar; Tule Lake. TUOLUMNE CO.: Sonora Pass.
Seasonal flight period (Fig. 3). QUEENS (158): early March to late September. WORKERS (521): early June to late September. MALES (230): early July to late October.
Flower records. QUEENS (25): Composite 36%; Crucifcrac 24%; Gentianaccae 12%. WORKERS (163): Composite 32%; Leguminosae 16%; Ranunculaceae 12%; Capparidaceae 11%; Labiatae 10%. MALES (120): Compositae 96%. Total: 308 in 15 families with 32 genera as follows: Althaea: lq, 7w, Asckpias: 6w, Aster. 9m; Astragalus: lq; Babamorhim: lw, Brasska: lq; Chrysothamnus: lq, Uw, 26m; Clrshm: 7q, 15w, 12m; Ckome: 18w, Dalea: 4w; Delphinium: 20w; Eriogonum: lw, Frasera: 3q, 3w, GaiUardia: lw; Geranium: lm; Gutkrraia: lw, 2m; Heknhan: 3w; Hetianthus: 15w, 62m; Manubium: 7w, lm; Medh cago: 14w; Melilotus: 4w; Memtelia: 2q, 10w, Monarda: lw. Pen-station: lw. Salvia: 8w, lm; Senedo: 5w, 4m; Solatium: 2w, Sphaerakea: lq, lw, 2m; Stankya: Sq; Tamartx: 2q; Taraxacum: lq; Trifblium: 4w.
Discussion. B. morrisoni is most closely related to B. griseocollis and may be distinguished from it by
the characters mentioned in the discussion under that species.
This species occurs principally in transmontane California. Three California specimens are not listed in the above records because of the improbŽable validity of the data associated with them. The putative localities include Davis, Yolo Co.; Ahwahnee, Madera Co.; and Yosemite Valley, Mariposa Co. None of these localities have proŽduced additional specimens, and even if the bees were collected where the labels indicate, they may have been accidental introductions without species establishment and therefore of little biogeographical importance.
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.
D escription. Queen. Length, 22.5 mm; width at wing bases, 11.0 mm; abdomen, 11.5 mm, width across T2, 11.5 mm; front wing length, 20.0 mm, width, 6.5 mm. Head: Frontal outline (excluding mouthparts) roundly trapezoidal, its median height nearly equal to the widest dimension, the temples rather sharply rounded, vertex straight to weakly arcuate; vertical region for the most part flat, not strongly inclined toward occiput; mostly covered with small and medium punctures; ocular half of ocellocular area with small and medium punctures, the ocellar half largely impunctate; compound eyes nearly equally rounded below and above, their inner margins subparallel and only slightly convergent above; ocelli rather large, positioned in a weak arc distinctly below the supraorbital line, much closer together than their diameters, the interocellar line only a little more than the ocellocular line, malar space about as long as distance between (and including) mandibular articulations, nearly flat and sparsely punctate; labrum little more than twice as wide as greatest thickness, its ventral margin arcuate, the shelf rather short and not sharp, the tubercles rather trans versely subconical and irregularly punctate with mesal summits well separated by a shallow intertubercular depression; flagellum nearly 11 times longer than scape, FI nearly equal to the combined lengths of F2 and F3, the latter noticeably longer than quadrate F2; clypeus rather evenly but not strongly convex, well covered with small and medium punctures, its median height about equal to the widest portion near base. Legs: Mesobasitarsite rectangular, 3 times longer than its widest part which is somewhat less than longest proximal hairs of the posterior fringe, the outer surface with shallow longitudinal concavity, the distal angles not sharp, about equally extended with shallow emargination between; outer surface of hind tibia microscopically granulose, with weak longitudinal convexity mostly anteriad of the middle; metabasitarsite rectangular, about 21 times longer than its average width and about twice as wide as the longest hairs on the basal half of the posterior margin, its outer surface broadly concave longitudinally, the blunt distoanterior angle noticeably in recess of the sharper dis- toposterior angle with a shallow emargination between, the posterior margin evenly but not strongly arcuate from base to distal end. Pubescence: Short, dense, and even except somewhat
longer and looser on the posterior margin of scutellum and on most of the venter and abdominal T4-5; mesobasitarsal posterior fringe not especially dense, largely composed of straight hairs of medium length basally gradually becoming very short distally; the corbicular fringe rather dense and composed mostly of straight to weakly arcuate hairs of medium length; metabasitarsal posterior fringe not dense, composed mostly of weakly arcuate hairs of medium length along the proximal two-thirds of the margin, beyond gradually becoming shorter and straighter distally. Color: Vertex (except an intermixture of few black hairs), most of occipital area, thoracic dorsum including a lobe beneath and extending forward of tegula, abdominal T l - 2 and most of T3 (except black distolaterally and laterally) golden (or amber) yellow; remainder of head, thorax, and abdomen black; legs black. Wings rather deeply and uniformly stained with brownish black.
Worker. Length, 17.0 mm; width at wing bases, 7.0 mm; abdomen, 9.0 mm, width across T2, 7.5 mm; front wing length, 15.0 mm, width, 5.0 mm. Except for some minor differences in relative dimensions, the structural features of this caste are closely comparable to those given for the queen. Color like that of the queen but the yellow on abdominal T3 of one of the hypotypes almost completely covers this tergum (cf. under Comments). Wings usually somewhat lighter than those of the queen.
Male. Length, 17.5 mm; width at wing bases, 9.0 mm; abdomen, 9.0 mm, width across T2, 8.0 mm; front wing length, 16.0 mm, width, 5.5 mm. Head: Frontal outline (excluding mouthparts) roundly trapezoidal, its median height little less than its widest dimen sion, the temples rather sharply rounded, the vertex straight; vertical region mostly flat and well covered with small (mostly follicular) punctures, the temples rather narrow; ocelli large, situated in a very weak arc far below the supraorbital line, much closer together than their diameters; ocellocular area mostly smooth, not as wide as the diameter of a lateral ocellus, the ocellocular line only about i the interocellar line; compound eyes bulging, their inner margins nearly parallel, nearly equally rounded below and above; malar space noticeably shorter than the distance between (and including) mandibular articulations, transversely weakly convex and with some small punctures; labrum little more than 2 times wider than its greatest thickness, the ventral margin straight except arcuate at lateral corners, the callosities weak and with few small punctures, separated only by a very shallow depression; flagellum about 3 times longer than scape, FI and F3 equal, each about li times longer than rectangular F2. Legs: Meso basitarsite subrectangular, nearly 4 times longer than the widest part which is about $■that of longest hairs on the weakly arcuate posterior margin, the distal angles both blunt, disto anterior one extends only slightly more than distoposterior one with only a very weak emar gination between, its outer surface only weakly concave longitudinally; metabasitarsite more rectangular, its outer surface weakly and broadly concave longitudinally, its widest part only slightly greater than length of longest hairs of the posterior fringe, the distal end nearly truncate. Pubescence: In character similar to that of the female except somewhat longer and looser on most of the abdomen; mesobasitarsal posterior fringe not dense, composed of mostly straight to weakly arcuate hairs that are longest on the basal half, gradually becoming short distally; metabasitarsal posterior fringe not dense and most of the hairs are more strongly arcuate, rather long on the entire margin except at the distal end. Genitalia and seventh and eighth abdominal sterna (PL XVI). Color: Similar to that of the female except for the following: Head mostly yellow with some black intermixed on the face and temples above eyes; all of abdominal T3 and a small amount on the basal middle of T4 yellow; legs black except some pile on the hind trochanters and considerable on the hind femora is yellow. Wings uniformly infumated but considerably paler than those of the queen.
Comments. No troublesome structural variation was detected in this species. Workers range in size from those that are considerably smaller to individuals that are virtually impossible to separate from genuine queens. Chromatically there is some variability to be noted, especially in the workers and males; in the former, abdominal T3 might be completely covered with yellow and a limited amount might occur on T4. In the male, abdominal T4 might be mostly if not completely covered with yellow, and some pallid pile might be apparent on the abdominal venter as well as some few intermixed yellowish hairs on the front and middle legs especially on the femora. Despite these variations this is one of the most stable and among the easiest species to identify.