Extracted from Bumble Bees and
Cuckoo Bumble Bees of California by Thorp, R. (1983).
Bombus nevadensis Cresaon, 1874, Trans. Amer. Enlomol. Soc, 5:102. q.m. Leclotype q, Nevada (#2637, ANSP) (selected by Cresson, 1916).
Bombus nevadensis miguelenta Cockerell, 1937, Pan-Pat Ento-mol., 13:148. ra. Holotype m, San Miguel Island, Santa Bar¬bara Co., California (#4649 CAS).
Bombus crotcfttl semlsuffusia Cockerell, 1937, Pan-Pac. Entomol., 13:148. q. Holotype q, San Miguel Island, Santa Barbara Co.. California (#4650, CAS).
Geographic range (Map 1). W. of 100° longitude, from western Nebraska W to California and N lo Saskatchewan and Yukon Territory (Canada). The eastern subspecies auncomus continues to the East Coast from Massachusetts to Florida.
California records. H UMBOLDT Co.: Eureka; Mad River beach; Shively. INVO Co.: Long Valley. LASSEN CO.: Blue Lake; Hallelu¬jah Junction; Susanville. MODOC CO.: Alturas, and 8 km E; Cedar Pass, 5 km NE*. Cedarvilte: Davis Creek; Goose Lake Valley; Hackamore; Lake City; Likely; Newell; New Pine Creek. MONO CO.: Bridgeport; Crestview, 17.5 km S; Crooked Creek, White Mtns.; Fates Hot Springs; Grant Lake; Leavitt Meadows; Mill Creek Canyon; Mono Lake; Pick el Meadow; Sonora Junc¬tion; Topaz Lake. NEVADA CO.: Truckee. PLUMAS Co.: Quincy, 6.5 km W. SANTA BARBARA Co: San Miguel Island. SHASTA CO: Shingletown. SIERRA CO.: Sierraville. SISKIYOU Co.: Etna; Tule Lake. TRINITY Co.: Helena. TUOLUMNE Co.: Mt. Dana; Sonora Pass.
Seasonal flight period (Fig. I). QUEENS (104): early April to lale September. WORKERS (81): late May to late September. MALES (13): early July to late August.
Flower records. QUEEHS (19): Lcguminosae 58%; Compositae 10%; Sanifraguceae 10%. WORKERS (33): Lcguminosae 64%; Compositae 21%; Labialae 12%. MALES (1): Leguminosae. Total: 53 in 7 families with 14 genera as follows: Althaea', lq, Iw; Astragalus: 4q, 6w; Babamorhiza: lq; Ceanothus: lq; Clrsium: lq, 3w; Heliantfius: 4w; Lupinus: lq; Medicago: lm; Melilona: 13w; Mentha: lq, 4w; Mexmbryantheimtm: lq; Ribes: 2q; Thermopsis: lq; Vkkr. 5q, 2w.
Discussion. B. nevadensis is not closely related to other California Bombini. It is recognized by the characters given in the subgeneric diagnosis. Stephen (1957: 61) was "inclined to question the conspecificity of this form (c semisuffusus) with the typical crotchit* mainly on the bais of its much longer malar space. The type of semisuffusus in the California Academy of Sciences collection was examined by RWT, who found that in addition to the long malar space it has the long flagellomere 1 and fine, uniform clypeai punctation which makes it unquestionably a color variant of nevadensis and not of crotchii. The female of semisuffusus was col¬lected in the same locality and within two days of the male nevadensis migueknsis. Both resemble crotchii in color pattern; however, Cockerell (1937) correctly assigned the male because "The genitalia are of the B. nevadensis, not B. crotchii type.** Mil-liron (1971) correctly synonymized crotchii semisuffusus and nevadensis migueknsis as color vari-ants of nevadensis, but he provided no discussion supporting his action and did not include San Miguel Island or any coastal California localities in his distribution records.
This species exhibits considerable color variation. The most common female color pattern in Califor¬nia, the nominate form, resembles B. morrlsoni (cf. Figs. 131a, 134). It occurs principally from transmontane California E to 100° W longitude, where it is replaced by a darker eastern form, auri-comus (Robertson), which resembles B. pennsyl-vanicus. These two forms of nevadensis intergrade between 102° and 98° W longitude in Nebraska (LaBerge and Webb, 1962). The nominate form also grades into a darker color form in Humboldt County (Eureka, Mad River beach, Shively), some of which have the same color pattern as migueknsis from Santa Barbara County (San Miguel Island) (Figs. 131a, 131b). This intergradation and chromatic variability in the Humboldt County populations suggest the inappropriateness of using a subspecific epithet for the coastal California popula¬tions. These coastal forms resemble B. crotchii and "nigroscutatus" populations of B. occidentalism especially in the females (cf. Figs. 130,140a).
The San Miguel Island population is geographi¬cally isolated from other nevadensis. The nearest coastal populations with the color pattern of migueknsis are over 72S km NNW in Humboldt County. The nearest populations, almost 320 km ENE in Inyo County, are of the nominate color pat-tern. It appears then that the migueknsis form represents a disjunct relict of the northern coastal populations.
The biology of the nominate form is discussed by Hobbs (1965a), and Frison (1917, 1918) dis¬cussed the biology of auricomus. Hobbs (1965a) found that Psithyrus insularis and P. suckkyi established in nests, and that Physocephab texana (Williston) parasitized adults of B. nevadensis in Alberta, Canada.
Extracted from A MONOGRAPH OF THE WESTERN HEMISPHERE BUMBLEBEES (HYMENOPTERA: APIDAE; BOMBINAE)by Millrion, H. (1971).
DESCRIPTION. Queen. Length, 22.0 mm; width at wing bases, 10.0 mm; abdomen, 11.0 mm, width across T2, 7.0 mm; front wing length, 19.5 mm, width, 8.0 mm. Head: Frontal outline rather elongate trapezoidal (excluding mouthparts), perceptibly wider than high, broadly rounded laterally above; vertical region slightly concave only about ocelli, the ocular one-third of ocellocular area with medium irregular punctation, the ocellar two-thirds smooth and polished, the vertical area posteriad of ocelli irregularly sculptured with medium punctures; outline of compound eye somewhat more broad below than above, the inner margin only slightly concave (outwardly) dorsally, each eye about one-fourth higher than wide; ocelli rather large, much below supraorbital line, situated in a weak arc, each much closer together than their diameters, which combined are about equal to ocellocular line; clypeus nearly as wide as high, more strongly convex above than below, entirely covered with dense rather uniform small punctures [there is, to me, no other species of bumblebees whose clypeus is so uniformly scupltured]; labrum little more than 2i times wider than thick, roughly and irregularly sculptured above, with weak "tubercles" nearly confluent medially, ventrad rather flat to the abrupt narrowly elevated margin; malar space about H longer than distance between (and including) mandibular articulations, its surface irregularly convex with noticeable pubescence on the posterior half; flagellum twice the length of scape, Fl two and one-half times as long as distal width, subequal to subquadrate F2, F3 and subrectangular F4 combined. Legs: Mesobasitarsite elongate rectangular, distally subtruncate, the disto-posterior angle short spinate, its outer surface moderately concave mid-longitudinally; outer hind tibial surface finely alutaceous, posteriorly broadly but weakly concave; metabasitarsite nearly 3 times longer than widest dimension, the posterior margin weakly nearly evenly arcuate from base to distal end, the base almost as wide as distal end, its outer surface shallowly concave, distally weakly emarginate with slightly acute disto-posterior angle somewhat more extended than disto-anterior angle. Pube-scence: On thorax rather short, dense and even throughout, somewhat longer, looser and more uneven on head, most of scutellum and on abdomen; corbicular fringe rather long and loose; metabasitarsal posterior fringe composed of long, arcuate well-separated hairs on basal two-thirds, longest hairs nearly equal to widest dimension of segment, the distal one-third with few short reclining hairs. Color: Head black with some admixture of yellow on vertex, moreso on postocciput. Thorax above and ventrally extended lobe anteriad of tegulae light ochraceous yellow, remainder and legs black. Abdominal Tl (except predominantly black at anterior corners and medially), T2-3 light ochraceous yellow, remainder of abdomen black. Wings rather deeply evenly infumated with chocolate brown.
Worker. Length, 17.0 mm; width, at wing bases, 8.0 mm; abdomen, 10.0 mm, width across T2, 7.0 mm; front wing length, 16.0 mm, width, 5.5 mm. Structural features of this average worker relatively very similar to those of the average queen. Pubescence: Physical character¬istics as in queen. Color: Head black except conspicuous intermixture of yellow on face, vertex, and postocciput; yellow on thoracic dorsum extended somewhat farther ventrad of tegulae than in queen, noticeable intermixture of black on mesothoracic disc, and abdominal Tl-3 entirely somewhat paler; otherwise colored as in queen, except wings slightly less infumated.
Male. Length, 19.0 mm; abdomen, 10.0 mm, width across T2, 7.5 mm; width at wing bases, 8.5 mm; front wing length, 14.5 mm, width, 5.0 mm. Head: Frontal outline triangulate ovoid (excluding mouthparts), only slightly wider than high; compound eye swollen, about three times higher than wide, the inner margin only weakly concave outwardly, divergent (in relation to same margin of opposite eye) dorsally, outline broadly arcuate posteriorly, above broadly rounded, ventrally more narrowly so; vertex very weakly convex, shallowly irregularly sculp-tured; ocelli positioned as weak arc below shortest inner margins of compound eyes and far below supraorbital line, removed from each other about as far as their diameters, interocellar and ocellocular lines nearly equal; malar space very short, not longer than distance between (and including) mandibular articulations; labrum noticeably less than twice as wide as thick, covered with strong and fine hairs but without prominent lateral callosities, its ventral margin broadly arcuate; flagellum 2i times longer than scape, Fl about twice as long as its distal thick¬ness, much longer than subquadrate F2 or rectangular F3, equal to combined lengths of two latter segments. Legs: Mesobasitarsite elongate rectangular, little more than 3 times longer than widest dimension, its subacutely rounded disto-posterior angle much in recess of the more acutely rounded disto-anterior angle, the alutaceous outer surface moderately concave mid-longitudinally; metabasitarsite slightly more than twice as long as greatest width, the disto-posterior angle subacutely rounded and recessed with relation to the subacutely rounded disto-anterior angle, the outer alutaceous surface only weakly but sharply narrowly concave on disto-posterior half, the posterior fringe long (longest hairs exceeding widest dimension of segment), the pubescence on outer surface moderately short, numerous, recumbent. . Pubescence: That on head and thorax shorter and somewhat denser than in the female; pile on abdominal Tl-2 similar to female in length and texture, longer on T3-7. Genitalia, seventh and eighth abdominal sterna (PI. XI). Color: Head (except for admixture of some black), thorax, legs (mostly), and abdominal Tl-3 pale ochraceous yellow; T4 with some black inter¬mixed on its basal half, but otherwise pale ochraceous yellow; T5 mostly black medially, pale ochraceous yellow laterally and distally; T6-7 rufous yellow. Wings moderately evenly stained with some brown as in the worker.
Redescribed from hypotypes. Queen, Chenney [Heeney ?] G[u]l[c]h, Colforado], 5-15 [HEM]; worker, Jacob's Cabin, Hart M[out]t[ain], Lake Co[unty], Ore[gon], elevation 6600 ft, July 9, 1937, Bolinger-Jewett [HEM]; male, Plainview, Jeff[erson] Co[unty], Colo[rado], 7-8000 ft, VII-9-14, 1927, (Brooklyn Museum Coll[ectio]n, 1929) [USNM].
TYPE. Examined a Cresson (1916: 125) lectotype 9 (No. 2637) in the collection of the Academy of Natural Sciences of Philadelphia.
TYPE LOCALITY. Nevada, U.S.A. Number of specimens at hand: 72. In flight: late April to the first half of September, the males making an appearance in early July. Distribution: (vertical), from near sea level to 11,000 ft; (horizon¬tal), Alaska to southern Mexico (Hidalgo); eastward in the United States to Wis¬consin. Recent examination of additional material not tabulated herein has extended the range considerably inland in British Columbia and western Alberta. Adjustment for this has been made on Map 5. Floral visitations: Cirsium, Crepis, Melilotus, and Trijolium. Lutz and Cockerell (1920) have added or compiled: Achillea, As¬tragalus, Cleome, Delphinium, Malvastrum, Monarda, Polemonium, Senecio, Sicyos, and Solidago. LaBerge and Webb (1962) listed Helianthus, Medicago, and Verbena as additional records.
COMMENTS. Disregarding size variability within the castes, the species neva-densis is otherwise remarkably constant in its morphological features except, per¬haps, for length and compactness of pubescence. Chromatically, however, the species does show considerable range in respect to the thoracic dorsum and abdominal Tl in both this and the following subspecies. Sometimes females of the nominate sub¬species have considerable black on the thoracic disc and abdominal Tl, and often the interalar area is predominantly black, depicting a rather sharp, wide interalar black band. A female (queen) n. nevadensis has been seen taken as far southward as about 50 miles northeast of Mexico City in the state of Hidalgo; this specimen has longer and looser pile, the lighter of which is duller throughout. Some specimens of the nominate subspecies from the lower coastal areas of the Northwest (British Columbia) grade into almost entirely black (melanics). Large series of both sub¬species reveal a continuous range in size from the smallest workers to the smallest queens. In some general locations where this and the following subspecies are allopatric, hybridization occurs (c/. under n. auricomus).
Bombus nevadensis auricomus
DESCRIPTION. Queen. Structurally [including physical appearance of pubescence] like that of the nominate subspecies. Color: Head black except for slight admixture of canary yellow above antennal bases, moreso on vertex and occiput. Thorax black, except pronotum, meso-scutum including upper part of mesopleurum anteriad of wing bases deep yellow, with noticeable admixture of ochraceous yellow over posterior scutellar half. Abdominal Tl black, T2 (except for scattered black hairs basally) and T3 covered with light ochraceous yellow; T4-6 black. Wings uniformly deeply infumated with blackish brown.
Worker. Smaller but structurally much as in the queen. Color: As in the queen except the yellow on thorax and abdomen paler.
Male. Morphologically like n. nevadensis, including abdominal sterna and genitalia. Color: Head and thorax as in n. nevadensis except dorsum with moderately wide indefinite black interalar band. Wings less deeply infumated than in female. Abdominal Tl (mostly) -3 covered with ochraceous yellow, T4-7 black though some hairs laterally on T5-7 with tinge of burnt sienna.
REDESCRIBED FROM HYPOTYPES: Queen, Columbus, 0[hio], Aug. 13, 1947. H. E. Milliron [HEM]; worker, same data [HEM]; male, West P[oin]t, Nebraska], Aug. 17, '03, ["Oma weed"(?)L (Crawford, No. 312), J.C. Crawford [HEM].
TYPE. Examined—my (1959, unpub.) lectotype 5 (mounted in copula with a conspecific male) bearing Robertson's notebook number 19944 (referring to Carlinville, 111., July 19, 1897), is a part of the Theodore H. Frison Collection, Illinois Natural History Survey, Urbana. A penciled label on the pin indicated that K. Sommerman had previously designated this female as a " $ lectotype", but such information was never published. The pin also bears what is presumed to be Robertson's red "type" label; evidently he meant this male to be the type because he established Bombias on the basis of that sex of auricomus. However, in conform¬ity with Cresson's type of the species (a $, n. nevadensis, 1916: 125) the above large worker was selected by me as the lectotype of the subspecies auricomus.
TYPE LOCALITY. Carlinville, 111., U.S.A. Number of specimens at hand: 99. In flight: late April to early September, the earliest appearance of males ca. mid-July. Distribution: (vertical), sea level to 4500 ft; (horizontal), Ontario, and Massachusetts south and southwestward to Texas, northward to the Dakotas. Recent examination of additional material not tabulated herein has extended the range into southern Ontario and considerably so northward in western Canada. Adjustment for this has been made on Map 6. Floral visitations: Epilobium and Pentstemon. From Lutz and Cockerell (1920) can be added: Asclepias, Antir¬rhinum, Astragalus, Carduus, Cnicus, Collinsia, Crataegus, Eupatorium, Fragaria, Helianthus, Mertensia, Phlox, Pyrus [Malus ?], Ribes and Vernonia. Additional records from Robertson (1929) are: Achillea, Aesculus, Agastacha, Aster, Bidens, Brauneria, Blephilia, Camassia, Cardamia, Cassia, Cephalanthus, Cercis, Cicuta, Cirsium, Claytonia, Clematis, Cornus, Delphinium, Desmodium, Dicentra, Dode-catheon, Gerardia, Hibiscus, Hydrophyllum, Ipomoea, Iris, Lactuca, Leonurus, Malva, Melilotus, Monarda, Nepeta, Oxalis, Petalostemon, Polemonium, Psoralea, Ptelea, Pycnanthemum, Robinia, Rosa, Rudbeckia, Scutellaria, Sisyrinchium, Soli-dago, Stachys, Tradescantia, Trifolium, Verbenia, Verbesina, Viola, and Zizia. Mitchell (1963) has added Ceanothus, Hypericum, Malus, and Rubus.
COMMENT. This is, in respect to the nominate subspecies, chromatically more variable. Sometimes females have the entire scutellum canary to light ochra¬ceous yellow with rather wide, distinctly limited black interalar band; and, on such specimens the pale pubescence extends farther ventrad on the mesopleurum ante-riad to wing bases. Often in the female all the thoracic dorsum is black except for yellowish pubescence on the pronotum and on the anterior margin of the meso-notum. Abdominal Tl in the female ranges from the usual black to almost com¬pletely yellow of various shades. The male might, or not, have any semblance of a distinct interalar black band, and often specimens of this caste have lateral pile on abdominal T5-7 distinctly tipped with burnt sienna.
Hybridization between the eastern and western subspecies frequently occurs in most allopatric locations, especially in broad expanses in the mid-western and northwestern United States and in certain southwestern areas of British Columbia (Canada). Often it is difficult to assign such hybrid specimens (especially males) to either subspecies.
The subgenus Bombias of Megabombus, represented by a single species, is restricted to the Western Hemisphere. I know of no very closely related species in the Eastern Hemisphere.