Extracted from Bumble Bees and Cuckoo Bumble Bees of California by Thorp, R. (1983).
Bombus crotchU Cresson, 1878, Proc. Acad. Nat Sci. Phila., p. 184. q. Lectotype q, California (#2168 ANSP) (selected by Cresson, 1916).
Geographic range (Map 4). Central California to Baja Califor¬nia del Norte, Mexico.
California records. ALAMEDA CO.: Berkeley, Pteasanton; San Leandro. CONTRA COSTA CO.: Antioch; Moras*; ML Diablo. FRESNO CO.: Coalinga, 6.5, 11, and 23 km W; Firebaugh, 10 km NW; Five Points; Fresno; Huntington Lake; Jacolitos Canyon; Little Panoche Canyon; Mercey Hot Springs, 8 km E; Orange Cove, 6.5 km N; Oxalis; Panoche; Parlier, Piedra; Trimmer, 11 km SW and 27 km E; Trimmer Springs; Walts Valley. GLENN CO.: Artois; Orland. IMPERIAL CO.: Brawley. INYO CO.: Haiwee; Lone Pine; Owens Lake; Pine Creek. KERN CO.: Arvim Bakersfield, and 24 and 29 km E; Caliente, 5 km S; Camelo JcL; Cummings Valley; Frazier Park, 2 km S; Fort Tejon; Kern Canyon; Keraville; Lebec; McFarland, 14 km E; McKittrick, 16 km E; Mill Potrero; Mojave, 13 km W; Rosamond; Shafter, Tart; Tehachapi, and 39 km W; Wheeler Ridge; Woody. Los ANGELES Co.: Altadena; Azusa, 5 km N, San Gabriel Canyon; Baldwin HQIs; Big Pines, Angeles NatL For.; Big Rock Public Camp, Angeles Natl. For.; Castak. 16 km N; Claremont; Devils Gate Dam, Flint Ridge; El Segundo; El Segundo Sand Dunes; Glendale; Gorman, and 6 km E; Griffith Park; Jonsons Peak; Litucrock; Llano, and 8 km SE; Los Angeles; ML San Antonio; Newhall; Pasadena; Palmdale; Pomona; Santa Monica; Tanbark Flat; Walnut; Westwood Hills; Whittier. MADERA CO.:
Nipinnawasee; San Joaquin Experimental For. MARIPOSA Ca: Exchequer Dam; Wawona. MERCED Ca: Delhi, 3 km S; Dos Pakw; Livingston; Merced Falls, 6 km SE; West Panoche Hills. MONTEREY Ca: Arroyo Seco Camp; King City, 14 fan E; Soledad. ORANGE Ca: Costa Mesa; Laguna Beach; Newport Beach; Santa Ana; Yorba Linda. RIVERSIDE Ca: Ansa, 6 km W; Banning; Corona; the Gavilan, 610 m; Hemet; Magnesia Canyon; Palm Springs; Penis, and 2 km W; Sage, 10 km W; Sunnymead, 13 km E; Temecula. SACRAMENTO Ca: Sacramento. SAN BENITO Ca: Bitterwater, 8 km S; Idria, 10 km SE SAN BER¬NARDINO Ca: Bear Valley; Bloommgton; Cushenbury Spring, San Bernardino Mtns., 1220 m; Kramer Hills; Loma Linda; Mojave River, near Deep Creek, Mojave Desert; Morongo Val¬ley; Ontario; Phelan; Seeley Flat, San Bernardino Mtns.; Sidewinder Well, Mojave Desert; VerdemonL SAN DIEGO Ca: Anza-Borrego State Park; Banner, 5 km E; Borrego; Carbbad; Encinitas; La Mesa; Lake Henshaw; Ramona; Santa Ysabel; Spring Valley; Warner Ranch; Warner Springs. SAN JOAQUIN Ca: Tracy. SAN LUIS OBSTO Ca: Atascadero; Paso RoMes; Pozo, 16 km E; Sbandon, 11 km SW. SANTA BARBARA Ca: Aliso Canyon, 10 km SW New Cuyama; Cachuma Lake, 5 km W; Carpenteria; Cuyama; Cuyama Valley, Goleta; San Marcos Ranch Hdqtrs.,
Santa Inez Mtns.; Santa Barbara; Santa Rosa bland. SANTA CLARA Ca: Palo Alto; San Antonio Valley, San Jose. SONOMA Ca: Cloverdate; Sonoma. STANISLAUS Ca: Newman; Patterson; Turteck, and 16 km E. TEHAMA Ca: Red Bluff. TULARE Ca: Ash Mt, Sequoia NatL Park; Bubbs Creek; Idtewild; Kaweah; Kings Canyon; Lemoncove; Mineralking; OrosU Porterville; Sequoia NatL Park; VTsalia; Woodlake. TUOLUMNE Ca: James¬town; Oakland Recreation Camp; Rawhide. VENTURA Ca: Camarino; Hungry Valley, 8 km S Gorman; ML Pinos; Ojai; Santa Paula, Ventura. YOLO Ca: Davis.
Seasonal flight period CRg. 4). QUEENS (225): late February to late October. WORKERS (349): late March to late October. MALES (122): late May to early September.
Fbwer records. QUEENS (50): Leguminosae 36%; Labiatae 12%; HydrophyUaceae 10%. WORKERS (95): Leguminosae 36%; Asdepiadaceae 24%; Compositae 14%. MALES (41): Asdepiada-ceae 54%; Leguminosae 22%; Compositae 22%. Total: 186 in 15 families with 33 genera as follows: Amstndda'. 4q; Asckptas: 2q, 23w, 22m; Astragaha: 5q; Brassta: 3q, lw, Chaenactis'. lq, llw, Delphinium: 2w, Eriodkffon: 2w; Eriogonum: 3w; Eschschohki: 3q, 5w; Gutierrezta: lw; HeUanthm: 6m; Hemitonia'. 2m;
Hypericum: lw; Isomerb: 3q; Lantana: lq; Lamyna: lq, lw; Lepldospartum: lm; Lofta: 6w, lm; Luplmts: 6q, 92; Medkago: lq, 16w, 7m; Oenothera: lq; Orthooatpta: lq; Parkinsonia: lq; Penstemon: 7w, PhaceUa: 5q, 2w; Raphama: lq; Sofofe: 5q, 2w; SoUdago: lq, lw; Triehostema: lq; Trtfbmim: lq, lm; Wefa: 2w; Hfefcenfa: lm; Wfrfcrfa: 3q.
Discussion. B. crotchit appears most closely related to members of the subgenus Separate bombus. It can be separated from them by the char¬acters given in the subgeneric diagnoses.
The queen which Cockerell named 5. cro&fcff semisuffitsus is actually a female of 2?. nevadensis (see discussion for that species). Other infraspecific names represent extremes of infrapopulation color variants and do not merit subspecific rank.
Most color variation occurs in the amount of reddish hair on the apical metasomal tergites. In both sexes, reddish hair may be present on all tergites from the apex of tergite 3 to the last tergite, or replaced by black hair on one or all of these. Replacement by black hairs occurs from anterior to posterior.
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, 23.0 mm; width at wing bases, 10.5 mm; abdomen, 12.0 mm, width across T2, 12.0 mm; front wing length, 19.0 mm, width, 7.0 mm. Head: Frontal outline (excluding mouthparts) roundly trapezoidal, the widest part about equal to the median height, rather broadly rounded at the temples, nearly straight across the vertex to very weakly arcuate; vertical region flat, not strongly inclined toward occiput, and mostly covered with small and medium punctures; ocular half of ocellocular area with some small and medium punctures, the ocellar half mostly smooth; compound eyes nearly equally rounded above and below, their inner margins subparallel; ocelli rather large, situated in a weak arc much below the supraorbital line and closer together than their diameters; interocellar line noticeably longer than ocellocular line; malar space about as long as the distance between (and including) mandibular articulations, mostly weakly convex and with few punctures; labrum little more than twice as wide as its greatest thickness, its ventral margin arcuate, the shelf short but moderately prominent, the tubercles rather concave below, mostly coarsely punctate, their mesal summits separated by a moderately deep intertubercular depression; flagellum twice as long as scape, FI equal to the combined lengths of F2 and F3, the latter considerably longer than quadrate F2; clypeus rather evenly but not strongly convex medially and slightly slanted laterally, mostly covered with very small inconspicuous punctures, its median height about equal to the length of widest part near base. Legs: Mesobasitarsite almost rectangular, nearly 5 times longer than its widest part which is about equal to the length of longest hairs of posterior fringe, the distal angles not sharp and about equally extended with a shallow emar- gination between, the outer surface nearly flat; outer surface of hind tibia weakly convex mid-longitudinally, the entire surface microscopically granulose; metabasitarsite with outer surface shallowly concave longitudinally, much wider than longest hairs of posterior fringe, the posterior margin evenly arcuate from base to distal end, the sharper distoposterior angle extended somewhat beyond the distoanterior one with a shallow emargination between. Pubescence: Moderately short and only slightly longer on vertex, posterior margin of scutellum, on penultimate and antepenultimate abdominal terga, rather fine and dense, that on abdominal T2 (usually) with a noticeable median notch; mesobasitarsal posterior fringe of medium length but not dense on basal half, short beyond; hind tibial posterior fringe composed mostly of rather long and dense straight to weakly arcuate hairs; posterior fringe of metabasitarsite on the proximal half of this segment consists of straight to weakly arcuate hairs of medium length, not dense, becoming very short on the distal half. Color: Occiput (mostly, cf. under Comments), thoracic dorsum anteriad of tegulae continuous with a more or less circular patch on the upper part of the mesopleuron and abdominal T2 (except basally, especially medially, black) golden-yellow; remainder of head, body, and legs black (except sometimes parts of distal abdominal terga with some rufous, cf. under Comments). Wings rather deeply and uniformly infumated with brownish black, with slight violaceous reflection under certain light.
Worker. Length, 16.5 mm; width at wing bases, 8.0 mm; abdomen, 8.0 mm, width across T2, 8.0 mm; front wing length, 15.0 mm, width, 5.0 mm. There seems to be little deviation from characteristic structures detailed for the queen except that in this caste these features are relatively smaller or less in proportions; it should be noted that usually the clypeus is more coarsely and less densely punctate; type of pubescence is about the same. Color: Head and thorax with color and pattern much as in the queen; abdominal T1 usually black but some times with a slight amount of pale (yellowish) intermixed laterally, T2 is generally all yellow, at least the distal part of T3 and all of T4-6 bear pile of faint reddish yellow to burnt sienna; at least traces of this latter color might occur on the legs (especially on the coxae, trochanters, and beneath on the femora). Wings usually somewhat paler than those of the queen.
Male. Length, 17.0 mm; width at wing bases, 8.5 mm; abdomen, 8.0 mm, width across T2, 7.5 mm; front wing length, 16.0 mm, width, 5.0 mm. Head: Frontal outline (excluding mouthparts) roundly trapezoidal, noticeably wider than its median height, the narrow temples rather sharply rounded, transversely straight to weakly arcuate across the vertex; vertical region flat and mostly covered with medium (follicular) punctures; ocelli large and much closer together than their diameters, situated in an arc much below the supraorbital line; ocellocular area distinctly less in width than £ the diameter of an ocellus, and the ocellocular line nearly £ the interocellar line; compound eyes bulging, much more broadly rounded above than below, their inner margins nearly parallel being only slightly divergent below; malar space noticeably shorter than distance between (and including) mandibular articulations, its surface weakly convex transversely and with few small punctures; labrum nearly twice as wide as its greatest thickness, the ventral margin nearly straight except rounded at the corners, the callosities weak and separated by only a shallow depression; flagellum little more than 3 times longer than scape, FI about equal to F3 which is nearly 1£ times longer than rectangular F2. Legs: Mesobasitarsite elongate-subrectangular, about 4 times longer than its widest part which is somewhat less than the length of longest hairs of the posterior fringe, the outer surface nearly flat, the distoanterior angle extending considerably beyond the smaller somewhat blunter distoposterior angle with shallow emargination between; metabasitarsite more nearly rectangular than mesobasitarsite, its widest part equal to about f the length of the longest hairs of the posterior fringe, the outer surface only weakly concave longitudinally, the distal end subtruncate. Pubescence: In character very similar to that detailed for the queen; mesobasitarsal posterior fringe not dense, the hairs along the proximal half of margin medium in length and straight or nearly so gradually becoming very short beyond; much of the outer surface of hind tibia noticeably bare of pile; metabasitarsal posterior fringe loose and composed of rather long mostly weakly bent hairs, most of which near the distal end being only slightly shorter. Genitalia and seventh and eighth abdominal sterna (PI. XVI). Color: Face and vertical region (except sometimes with few black hairs on the former and just above eyes on temples), occiput, and most of genae golden-yellow; thoracic dorsum including a small down ward extension onto pleuron anteriad of wing base golden-yellow except for a black interalar band of medium width; legs and venter mostly black; abdominal T1 (m ostly), and T2 golden-yellow, T3 mostly black but often with at least traces of yellow laterally or disto- laterally, T4 black but sometimes similarly colored as on T3, T5 black but usually with at least some burnt sienna distally, T6-7 bearing burnt sienna pile (cf. under Comments). Wings considerably paler than those of either queen or worker.
Comments. Aside from discernible differences in punctation on the female clypeus and body size, little structural variation is noted. Color variability is, how ever, considerable in all castes especially with respect to that on the abdomen. The form regarded as typical has most of the pile on abdominal T4-6 (and sometimes distally on T3) ferruginous or burnt sienna in both queen and worker, and the amount of black on T2 varies from a small amount basally to a much greater amount especially mid-basally; this is the form described by Cresson (1878: 184), and by Provancher (1888: 342) under the name nigrocinctus. Often a form
(especially of the queen) occurs having abdominal T3-6 mostly or entirely black; this is the form described as variety nigricaudus by Prison (1927c: 375). The male is even more variable on its abdomen and to some extent with respect to the width and definity of the interalar black band; abdominal T3-4 frequently black but often with considerable yellow laterally especially distolaterally, and sometimes the amount of burnt sienna (or ferruginous) distally on T5 is more extensive, quite conspicuous.
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