67 kinds match in US, CA COMPARE IMAGES

Bombus appositus  [popup] female queen Bombus appositus  [popup] female worker Bombus appositus  [popup] male Bombus californicus  [popup] female queen Bombus californicus  [popup] female worker Bombus californicus  [popup] male Bombus caliginosus  [popup] female queen Bombus caliginosus  [popup] female worker Bombus caliginosus  [popup] male Bombus centralis  [popup] female queen Bombus centralis  [popup] female worker Bombus centralis  [popup] male Bombus crotchii  [popup] female queen Bombus crotchii  [popup] female worker Bombus crotchii  [popup] male Bombus fervidus  [popup] female queen Bombus fervidus  [popup] female worker Bombus fervidus  [popup] male Bombus flavifrons  [popup] female queen Bombus flavifrons  [popup] female worker Bombus flavifrons  [popup] male Bombus franklini  [popup] female queen Bombus franklini  [popup] female worker Bombus franklini  [popup] male Bombus griseocollis  [popup] female queen Bombus griseocollis  [popup] female worker Bombus griseocollis  [popup] male Bombus huntii  [popup] female queen Bombus huntii  [popup] female worker Bombus huntii  [popup] male Bombus insularis  [popup] female Bombus insularis  [popup] male Bombus melanopygus  [popup] female worker Bombus melanopygus  [popup] male Bombus melanopygus  [popup] female queen Bombus mixtus  [popup] female queen Bombus mixtus  [popup] female worker Bombus mixtus  [popup] male Bombus morrisoni  [popup] female queen Bombus morrisoni  [popup] female worker Bombus morrisoni  [popup] male Bombus nevadensis  [popup] female queen Bombus nevadensis  [popup] female worker Bombus nevadensis  [popup] male Bombus occidentalis  [popup] female queen Bombus occidentalis  [popup] female worker Bombus occidentalis  [popup] male Bombus rufocinctus  [popup] female queen Bombus rufocinctus  [popup] female worker Bombus rufocinctus  [popup] male Bombus sitkensis  [popup] female queen Bombus sitkensis  [popup] female worker Bombus sitkensis  [popup] male Bombus sonorus  [popup] female queen Bombus sonorus  [popup] female worker Bombus sonorus  [popup] male Bombus suckleyi  [popup] female Bombus suckleyi  [popup] male Bombus sylvicola  [popup] female queen Bombus sylvicola  [popup] female worker Bombus sylvicola  [popup] male Bombus vandykei  [popup] female queen Bombus vandykei  [popup] female worker Bombus vandykei  [popup] male Bombus vosnesenskii  [popup] female queen Bombus vosnesenskii  [popup] female worker Bombus vosnesenskii  [popup] male

REMAINING (number with state)
ANSWER THIS FIRST! The Western portion of the guide is usable with caution, let us know if you have problems resolving any species
 2. Click here for guide for all species including western species (67)
 1. EASTERN - Click here for completed and well tested guide to eastern species (22)
Abdomen, T1, hair color, not counting the hairs present on the anterior portion of the segment that faces the propodeum
 All yellow or off-white (50)
 Light and dark hairs mixed or in patches (29)
 All black (23)
 With strong rust, brown, orange, red HIGHLIGHTS or all orange (16)
Abdomen, T2, hair color
 All yellow or off-white (43)
 With strong rust, brown, orange, red HIGHLIGHTS or all orange (33)
 Light and dark hairs mixed or in patches (32)
 All black (26)
Abdomen, T3, hair color
 All black (39)
 With strong rust, brown, orange, red HIGHLIGHTS or all orange (36)
 All yellow or off-white (30)
 Light and dark hairs mixed or in patches (29)
Abdomen, T4, hair color
 All yellow or off-white (43)
 Light and dark hairs mixed or in patches (41)
 All black (34)
 With strong rust, brown, orange, red HIGHLIGHTS or all orange (30)
 All PURE WHITE, NOT light yellow (2)
Abdomen, T5, hair color
 All black (55)
 Light and dark hairs mixed or in patches (37)
 All yellow or off-white (25)
 With strong rust, brown, orange, red HIGHLIGHTS or all orange (17)
 All PURE WHITE, NOT light yellow (5)
B. centralis vs. B. flavifrons
 B. centralis - Abdominal segment, T3 and T4 hair color completely or a mix of YELLOW, GOLD, OR ORANGE with no black hairs mixed in - scutum, hair color of anterior area, with exclusively or almost exclusively yellow hairs, although a few black hairs may be found intermixed with the dominant yellow hairs at the lateral edges, if so then the density of black hairs is clearly lower medially than laterally - scutellum, hair color, ranging from exclusively yellow to mixed yellow and black, if the latter then almost always with the black hairs restricted to the center of the scutellum and not mixed throughout all hair on the scutellum (2)
 B. flavifrons - Abdominal segment, T3 and T4 hair color often DARK but sometimes with extensive yellow or orange, however, even dark specimens have at least a few YELLOW OR ORANGE HAIRS ON THE APICAL RIM of the segment, if appearing to have entirely orange hairs then almost always with some black laterally on T3 or T4, note that ANY black hair here will suffice - scutum, hair color in anterior area, always with mixed yellow and black hairs, almost always with an equal density of black hairs throughout, if uneven then only slightly more dense laterally and with black hairs still clearly present medially - scutellum, hair color, highly variable, although the orange form of B. flavifrons seems to always have a significant amount of black hairs intermixed with the yellow hairs of the scutellum, most often with long black hairs present throughout and not restricted to the middle (2)
 B. centralis - Abdomen, T3 and T4 segment hair color ORANGE often bright orange - T5 hair color BLACK or often ORANGE (1)
 B. flavifrons - Abdomen, T3 and T4 segment hair color YELLOW, with T4 sometime half yellow and half black - T5 hair color always BLACK (1)
B. rufocinctus vs selected other species
 Others - Not as above, although it would be wise to compare possible rufocinctus specimens to long series of positively identified rufocinctus from the same general area in order to account for variation - Malar space is often the most reliable way to initially determine if a specimen IS NOT rufocinctus, any specimens with equal or greater malar spaces in comparison to the basal width of the mandible are very unlikely to be rufocinctus (8)
 B. rufocinctus - Head, malar space, the distance between the very bottom of eye and the mid-point of the attachment of the mandible always much shorter than the width of the base of the mandible, often appearing to be half that distance - Head, hair patch below antennal sockets, hair often but not always all black, if yellow hair is present then they are shorter, more sparsely distributed, and usually significantly more branched than the surrounding black hairs - Head, shortest distance between the lateral ocelli and the compound eye, usually equal to approximately 2-2.4 ocellar diameters in workers, slightly shorter in queens, closer to 1.6-2 ocellar diameters - Head, ocelli height in relation to the top of the compound eyes, slightly below the imaginary line that runs across the top of the eyes, but this is not a reliable character - Propodeum, surface texture, requires HIGH MAGNIFICATION, surface marked with very fine patterning which acts to diminish the integument s luster, this being most evident on the posterior, lateral faces of the propodeum found outside of the basal triangular enclosure - Abdomen, dorsal color patterning, females are tricky to identify because of the EXTREME variability of the abdominal colors, some individuals having a great deal of red on T2-4 while others have none or may exhibit such coloration only on a subset of these tergites, segments can be any combination of orange, yellow, or black, often intermixed on an individual segment, colors may vary even within a colony - Abdomen, T2, surface texture, requires HIGH MAGNIFICATION, surface marked with very fine patterning which acts to diminish the integument s luster, appearing either matte or only very slightly reflective, not distinctly smooth and shiny, punctures - Males, shortest distance between the lateral ocelli and the compound eye, of the 4 species with ocelli well below the tops of the eyes this species has lateral ocelli are 3 quarters to 1 ocelli width from the edge of the eye while the other species ocelli are almost touching the eye (3)
Female, B. appositus vs. B. frigidus vs. B. mixtus
 B. Appositus - Head, hair color PALE YELLOW and DENSE in the queen, normal in the worker but with scattered black hairs- Thorax, scutellum hair color usually ORANGE or orange-brown, but with some specimens hair color yellow instead - Abdominal T2 hair color YELLOWISH ORANGE to yellowish orange-brown - T3 hair color YELLOWISH ORANGE to yellowish orange-brown on tergites yellow is often restricted to along the rims of the segments (2)
 B. mixtus - Head, hair color above antennae YELLOW MIXED WITH SOME LONGER BLACK HAIRS - Thorax, scutellum hair color YELLOW or ORANGISH usually mixed with SOME LONGER BLACK HAIRS - Abdominal T2 hair color varies from YELLOW to ORANGE in the middle of the segment, with most specimens showing BLACK or darker colored hairs on the sides - T3 often all or mostly BLACK with yellow hairs along the apical rim, but some specimens can be all orange-yellow with either no black or only a narrow band along the base (2)
Female, B. appositus vs. B. sylvicola
 B. appositus - Head, space between mandible and base of eye DISTINCTLY LONG compared to width - Thorax, scutellum hair ORANGE to orange-brown to sometimes yellow - Abdominal T1 through T5 YELLOWISH ORANGE to yellowish orange-brown, yellow hairs often restricted to along the rim (2)
 B. sylvicola - Head, space between mandible and base of eye roughly equal to width of base of mandible - Thorax, scutellum hair color YELLOW with a wedge of black hairs in the center - Abdominal T1 hair color LIGHT - T2 and T3 hair color with extensive BRIGHT ORANGE though in some individuals the orange is faded to a pale orange - T4 and T5 hair color LIGHT (2)
Female, B. caliginosus vs. B. vandykei
 B. caliginosus - Abdominal T3 segment hair color BLACK - T4 segment hair color entirely YELLOW or with yellow along the apical rim - Abdominal sternites 3 and 4 hair color YELLOW apically - Sternites 2 and 5 hair color BLACK apically - Very hard to tell apart from B. vandykei and requires very close inspection of tergite and sternite hair coloring (2)
 B. vandykei - Abdominal T3 segment hair color YELLOW at least along the apical rim - T4 segment BLACK with scattered yellow hairs at times along the apical rim and the far sides - Abdominal sternites 2, 3, 4, and 5 hair color yellow apically (1)
Female, B. centralis vs. B. fervidus
 B. centralis - Specimens with all LIGHT or yellow facial hair - Hair on face above and below antennae all YELLOW or a few dark hairs mixed with significant amounts of light or yellow with no specimens showing all dark hairs - Hair directly behind ocelli all LIGHT or a few dark hairs mixed with significant amounts of light with no specimens showing all dark hairs - Abdominal hair color on T5 segment usually LIGHT AND DARK hairs mixed, with some specimens showing all black hairs - Overall hair color on both thorax and abdomen GOLDEN YELLOW or orangish - Generally strictly a western species, only found from of the ROCKY MOUNTAINS and to the WEST (2)
 B. fervidus - Specimens all with DARK or mostly dark facial hair with no specimens showing all light facial hair - Hair on face above and below antennae DARK or mostly dark with a small amount of light hair mixed in, with no specimens showing all light hairs - Hair directly behind ocelli BLACK or dark colored, with no specimens showing all light hairs - Abdominal hair color on T5 segment on all specimens showing BLACK hair, never yellow or orange hairs - Overall hair coloring on the both the thorax and the abdomen bright CANARY YELLOW - Found both EAST AND WEST of the Rocky Mountains (2)
Female, B. crotchii vs. B. mixtus vs. B. polaris
 B. crotchii - Head, malar space between mid-point of mandible and very bottom of eye compared to width of base of mandible SHORT - Hair color above antennae COMPLETELY BLACK - Thorax, scutellum hair color COMPLETELY BLACK - Abdomen, T1 segment hair color COMPLETELY BLACK- Primarily found in CALIFORNIA and neighboring states (2)
 B. mixtus - Head, malar space between mid-point of mandible and very bottom of eye compared to width of base of mandible SHORT to about equal - Hair color above antennae primarily YELLOW with a few insignificant black hairs mixed in - Thorax, scutellum hair color completely yellow to yellow with scattered black hairs - Abdomen, T1 segment hair color YELLOW - Overall appearance, normal bumblebee hair length - Primarily found from the THE ROCKY MOUNTAINS to the WEST, but with a very few specimens recorded in more eastern parts of North America (2)
Female, B. franklini vs. B. vandykei
 B. franklini - Facial hair color above antennae mix fairly equal mix of LIGHT AND DARK hairs, but with most specimens showing all dark hairs - Hair color above ocelli YELLOW - Thorax hair color on scutum YELLOW with a PATCH OF BLACK or no hair in the middle of the scutum, with the YELLOW hair extending basally past the front wing bases in the shape of an INVERTED U - Abdominal T3 and T4 segments hair color BLACK - Abdominal T5 segment hair color BLACK, with some specimens showing 2 small white or LIGHT COLORED SPOTS on either side of the segment - Very rare and hard to find specimen, thought to be endangered or possibly extinct, with the last documented specimen found in 2006, note that we only had 1 specimen of B. franklini to compare to and used information from http://www.xerces.org/franklins-bumble-bee/ for additional information. (2)
 B. vandykei - Facial hair color YELLOW, both above antennae and above ocelli, with only a few scattered black hairs on the outside edges of the hair patches - Thorax, scutum, hair color YELLOW from head to base of wings and BLACK hair extending basally - Abdominal T3 segment hair color YELLOW at least along the apical rim - T4 segment BLACK with scattered yellow hairs at times along the apical rim and the far sides - Abdominal T5 segment hair color ALL BLACK (2)
Female, B. frigidus vs. B. jonellus vs. B. sylvicola vs. B. mixtus
 B. mixtus - Head, hair color above antennae is YELLOW or primarily yellow - Abdominal T2 hair color varies from YELLOW to ORANGE in the middle of the segment, with most specimens showing BLACK or darker colored hairs on the sides - T3 often all or mostly BLACK with yellow hairs along the apical rim, but some specimens can be all orange-yellow with either no black or only a narrow band along the base (2)
 B. sylvicola - Head, hair color above antennae varies from YELLOW to primarily yellow - Abdomen, T2 and T3 hair color extensively BRIGHT ORANGE with some specimens showing only a faint orange color to sometimes nearly yellow, often, but not always with no black hairs present (2)
Female, B. huntii vs. B. sylvicola vs. B. melanopygus
 B. huntii - Head, malar space between mid-point of mandible and very bottom of eye compared to width of base of mandible SHORT or ABOUT EQUAL - Hair color above antennae COMPLETELY YELLOW to MIXED WITH BLACK- Thorax, scutum hair color YELLOW in front half and BLACK in rear half - Abdomen, T5 segment hair color COMPLETELY BLACK (2)
 B. melanopygus - Head, malar space between mid-point of mandible and very bottom of eye compared to width of base of mandible roughly EQUAL - Hair color above antennae usually appears primarily YELLOW but always has a significant amount of long black hairs intermixed among long yellow hairs and densely packed shorter yellow hairs in northern populations but usually all Yellow in the western ranges of the U.S. - Thorax, scutum, hairs are an intermixing of yellow and black hairs with black hairs predominating near the scutellum and light hair predominating towards the head, southern populations the lower half is usually entirely black and the upper a mix of yellow and black hairs - Abdomen, T5 hair color northern populations PRIMARILY BLACK usually with a few yellow hairs on the outer edges of the segment, southern populations with extensive yellow, black only retained in the central third of the segment (2)
 B. sylvicola - Head, space between mandible and base of eye roughly equal to width of base of mandible - Hair color above antennae BLACK to mixed black and yellow - Thorax, scutum, hair color YELLOW in front half and BLACK in rear half - Abdomen, T5 hair color YELLOW, or PRIMARILY BLACK with a few yellow hairs on the outer edges of the segment (2)
Female, B. melanopygus vs. B. morrisoni vs. B. sonorus
 B. melanopygus - The race of B. melanopygus within the range of these species has hair on the scutum that is black in the lower half and a mix of yellow and scattered black hairs in the upper - Hair color below base of front wing COMPLETELY YELLOW - Abdomen, T2-3 segments hair color BLACK - T5 segment hair color largely yellow with some black hairs (2)
 B. morrisoni - Thorax, scutum hair color YELLOW in front half and BLACK in rear half - Hair color below base of front wing BLACK WITH YELLOW PATCH right at the base - Abdomen, T2 segment hair color YELLOW - T3 hair color YELLOW with almost always a small amount of black on the far sides and along the apical rim (2)
 B. sonorus - Thorax, scutum hair color COMPLETELY YELLOW- Hair color below base of front wing COMPLETELY BLACK - Abdomen, T2 hair color YELLOW - T3 hair color YELLOW (2)
Female, B. mixtus vs B. sitkensis
 B. mixtus - T3 tends to be largely black with a thin border of light hairs along the rim - T4 almost always covered by completely light hairs (2)
 B. sitkensis - T3 tends to be entirely black - T4 tends to be largely black with at times a thin border of light hairs along the rim (2)
Female, Parasitic Species - Architecture of S6, when viewed from the side with specimen upside down - Note, the pattern of ridges and swellings on S6 is distinct to each species, but difficult to describe
 Highest point occurs approximately HALF-WAY between tip and base - In direct comparison, height is modest to low (1)
 Highest point occurs approximately ONE-THIRD of the way down from the tip - In direct comparison, height is greater, stongly angular and ridge-like (1)
Female, Queen, B. caliginosus vs. B. vosnesenskii
 B. caliginosus - Head, space between mid-point of attachment of mandible and very bottom of eye compared to width of base of mandible USUALLY LONG, but some specimens show shorter spaces - Very hard to tell apart from B. vosnesenskii, but has a very small distribution and is only found in COASTAL RANGES from northern Washington to southern California (1)
 B. vosnesenskii - Head, space between mid-point of attachment of mandible and very bottom of eye compared to width of base of mandible SHORT - Very hard to tell apart from B. caliginosus, which has a very limited distribution only in the coastal regions from northern Washington to southern California, and if the specimen is found outside of this range it is most likely B. vosnesenskii (1)
Female, Queen, B. centralis vs. B. huntii
 B. centralis - Malar space in comparison to B. huntii is often LONGER - Abdominal hair coloring over all appearance GOLDEN YELLOW, and appears darker directly compared to B. huntii - T1 through T4 hair color can vary from shades of yellow to reddish orange or a mix of yellows and oranges - Abdominal hair coloring of T2 segment in FRESH SPECIMENS is usually YELLOW with only a tinting of orange if at all, and hair color of T4 is usually bright ORANGE (1)
 B. huntii - Malar space in comparison to B. centralis is often SHORTER - Abdominal hair coloring distinct for each tergite segment and with little variance among specimens, and appears lighter and brighter than B. centralis - T1 segment hair coloring YELLOW - T2 and T3 segments distinctly bright ORANGE in appearance but mixed with significant amounts of yellow hairs - T4 segment hair color YELLOW - Abdominal hair coloring of T2 segment in FRESH SPECIMENS is usually ORANGE, and hair color of T4 is usually YELLOW (1)
Female, Queen, B. centralis vs. B. sonorous
 B. centralis - Hair on face above and below antennae all YELLOW or a few dark hairs mixed with significant amounts of light or yellow with no specimens showing all dark hairs - Hair directly behind ocelli all LIGHT or with only a few dark hairs mixed in with no specimens showing all dark hairs - Thorax hair coloring below base of front wing always all LIGHT or sometimes with an insignificant amount of darker hair mixed in -Abdominal hair coloring on T4 segment usually LIGHT or orangish, sometimes mixed with dark or black hair, with no specimens showing all black colored hairs (1)
 B. sonorous - Facial hair entirely dark - Thorax hair coloring below base of front wing usually all DARK with very small PATCH OF LIGHT hair directly adjacent to base of wing and pronotal lobe, with no specimens showing all light hair coloring -Abdominal hair coloring on T4 segment always BLACK, never all light or yellow in color (1)
Female, Queen, B. centralis vs. B. sylvicola vs. B. melanopygus
 B. melanopygus - Facial hair color LIGHT or LIGHT AND DARK MIX - Abdominal T2 hair color BRIGHT ORANGE - T3 hair color BRIGHT - T5 hair color BLACK (2)
 B. centralis - Facial hair color largely LIGHT with only scattered dark hairs, if any at all - Abdominal T2 hair color usually YELLOW with some darker gold - light orange hairs in the middle of the segment - T3 hair color usually the same - T5 hair color DARK with some specimens showing an insignificant amount of light colored hairs (1)
 B. sylvicola - Facial hair color LIGHT or LIGHT AND DARK MIX - Abdominal T2 hair color BRIGHT ORANGE or reddish - T3 hair color BRIGHT ORANGE or reddish - T5 hair color LIGHT with a few specimens showing an insignificant amount of dark hairs mixed in (1)
Female, Queen, B. griseocollis vs. B. morrisoni
 B. griseocollis - Facial hair of most specimens showing all DARK coloring usually with insignificant amounts of yellow hairs mixed in, however some specimens showing equal amounts of light and dark hairs mixed -Thorax hair coloring YELLOW, with distinct CIRCULAR PATCH OF BLACK hair or no hair on the basal center of the scutum - Thorax hair color below base of front wing COMPLETELY YELLOW or light colored - Hair color on T3 and T4 ALL BLACK with no specimens showing yellow or lighter colored hairs - Overall appearance of thorax and abdominal hair is much LESS DENSE than that of B. morrisoni - Found throughout the U.S. and Canada both in the East and West (1)
 B. morrisoni - Hair color above antennae ALL BLACK or, if yellow present, restricted to short hairs - Hair color above ocelli a mix of yellow and black hairs - Thorax hair color, on both the scutum and scutellum, completely YELLOW with no specimens showing circular patch of black or dark hair - Thorax hair color below base of front wing with a PATCH OF YELLOW hair directly adjacent to wing base apically with the rest of the hair COMPLETELY BLACK or dark colored - T3 hair color YELLOW with almost always a small amount of black on the far sides and along the apical rim - Abdominal T4 segment hair color BLACK with most specimens showing some yellow or light colored hair in the middle of the segment apically - Overall appearance of thorax and abdominal hair is much DENSER than that of B. griseocollis - Primarily a western species found from the ROCKY MOUNTAINS to the WEST with eastern specimens uncommon (1)
Female, Queen, B. morrisoni vs. B. nevadensis
 B. morrisoni - Facial hair color above ocelli a mix of yellow and black hairs - Thorax scutum hair color COMPLETELY YELLOW and hairs noticeably dense and relatively short - T3 hair color YELLOW with almost always a small amount of black on the far sides and along the apical rim - Primarily found in the WESTERN parts of North America with very few specimens found east of the Rocky Mountains (1)
 B. nevadensis - Facial hair color above ocelli DARK colored in some specimens or an even MIX of light and dark colored hairs - Thorax scutum hair color YELLOW WITH CIRCULAR PATCH OF BLACK or no hair in center - T3 hair color COMPLETELY YELLOW with no specimens showing black hairs on sides - Found throughout U.S. and Canada (1)
Female, Queen, B. morrisoni vs. B. rufocinctus
 B. morrisoni - Thorax, scutum hair color COMPLETELY YELLOW - Hair color below base of front wing BLACK WITH YELLOW PATCH right at the base - Abdomen, T2 segment hair color COMPLETELY YELLOW (1)
 B. rufocinctus - Thorax, scutum hair color YELLOW in front half and BLACK in rear half - Hair color below base of front wing COMPLETELY YELLOW - Abdomen, T2 segment hair color BLACK, ORANGE, or mix of YELLOW AND ORANGE, not completely yellow (1)
Female, Queen, B. morrisoni vs. B. sonorous
 B. morrisoni - Facial hair color above ocelli a mix of yellow and black hairs - Thorax scutum hair color COMPLETELY YELLOW - T3 hair color YELLOW with almost always a small amount of black on the far sides and along the apical rim - Primarily found in WESTERN North America with a few specimens found in Northern parts of Mexico (1)
 B. sonorous - Facial hair entirely dark - Thorax scutum hair color in most specimens YELLOW WITH A BAND OF BLACK colored hair running from tegula to tegula - T3 hair color COMPLETELY YELLOW - Primarily found in the SOUTHWESTERN U.S. and throughout Mexico and Central America (1)
Female, Queen, B. nevadensis vs. B. sonorous
 B. nevadensis - Facial hair color above ocelli ranges from all DARK to LIGHT AND DARK MIXED - Thorax scutum hair color all YELLOW or all YELLOW WITH A SMALL BLACK PATCH in center - T1 hair color can vary from BLACK TO YELLOW BUT USUALLY IS A MIXTURE - Found throughout North America (1)
 B. sonorous - Facial hair entirely dark - Thorax scutum hair color YELLOW WITH BLACK BAND across the rear running from tegula to tegula - T1 hair color always COMPLETELY YELLOW - Found primarily in the SOUTHWESTERN US and MEXICO (1)
Female, Worker, B. bifarius vs. B. sylvicola vs. B. melanopygus vs. B. rufocinctus
 B. rufocinctus - Head, malar space between mid-point of mandible and very bottom of eye compared to width of base of mandible always distinctly shorter - Head, hair color above the antennae PRIMARILY BLACK or YELLOW AND BLACK MIX - Thorax, scutum hair color YELLOW in front half and BLACK in rear half - Scutellum hair color YELLOW (1)
 B. sylvicola - Head, malar space between mid-point of mandible and very bottom of eye compared to width of base of mandible SHORT - Hair color above antennae BLACK sometimes with an insignificant amount of yellow hair mixed in - Thorax, scutum hair color YELLOW in front half and BLACK in rear half - Scutellum hair color YELLOW (1)
Female, Worker, B. moderatus vs. B. occidentalis
 B. nevadensis - T4 and T5 hair color DISTINCTLY DARK with no specimens showing lighter colored hairs - Overall body hair color GOLDEN YELLOW and THICK - Found throughout North America (1)
 B. occidentalis - T2 hair color completely BLACK or mostly black with some specimens showing some yellow or light colored hairs on the sides of the segment or on the basal edge - T5 hair color WHITE , YELLOW, OR LIGHT MIX (1)
Female, Worker, B. nevadensis vs. B. sonorous
 B. nevadensis - Facial hair color above antennae LIGHT AND DARK MIX - Facial hair color above ocelli LIGHT AND DARK MIX - Thorax scutum hair color all YELLOW or YELLOW WITH BLACK PATCH in center - Thorax hair color below base of front wing YELLOW or mostly yellow - Found throughout North America (1)
 B. sonorous - Facial hair color above antennae ALL DARK - Facial hair color above ocelli ALL DARK - Thorax scutum hair color YELLOW WITH BAND OF BLACK HAIR across center - Thorax hair color below base of front wing BLACK or mostly dark with small patch of lighter colored hair directly apical wing base - Found primarily in the SOUTHWESTERN US and MEXICO (1)
Female, queen, B. californicus vs. B. centralis
 B. californicus - Specimens all with DARK facial hair with no specimens showing all light facial hair - Hair on face above and below antennae DARK sometimes with insignificant amounts of lighter hairs mixed in - Hair directly behind ocelli BLACK or dark colored - Some specimens with scutellum hair color ALL BLACK - Abdominal hair color on T1 segment in some specimens all BLACK - Posterior apical angle of the basitarsus on the middle leg usually distinctly POINTED or SHARPLY ANGLED (1)
 B. centralis - Hair on face above and below antennae generally YELLOW or with only a few dark hairs mixed in - Hair directly behind ocelli LIGHT or with only a few dark hairs mixed in - Scutellum hair color always LIGHT, yellow, or orange colored, never all black - Abdominal hair color on T1 segment in all specimens COMPLETELY LIGHT, yellow, or orange colored, never all black - Posterior apical angle of the basitarsus on the middle leg often more or less ROUNDED or INDISTINCT although often this is difficult to determine without moving or removing hairs (1)
Female, worker, B. caliginosus vs. B. vandykei
 B. caliginosus - Abdominal T3 segment hair color BLACK - T4 segment hair color YELLOW - Abdominal sternites 3 and 4 hair color YELLOW apically - Sternites 2 and 5 hair color BLACK apically - Very hard to tell apart from B. vandykei and requires very close inspection of tergite and sternite hair coloring (1)
 B. vandykei - Abdominal T3 segment hair color YELLOW at least along the apical rim - T4 segment BLACK with scattered yellow hairs at times along the apical rim and the far sides - Abdominal sternites 2 through 5 hair color YELLOW along the apical rim - Very hard to tell apart from B. caliginosus and requires very close inspection of tergite and sternite hair coloring (1)
Female, worker, B. franklini vs. B. occidentalis
 B. franklini - Facial hair color above antennae mix fairly equal mix of LIGHT AND DARK hairs, but with most specimens showing all dark hairs - Hair color above ocelli YELLOW - Thorax hair color on scutum YELLOW with a PATCH OF BLACK or no hair in the middle of the scutum, with the YELLOW hair extending basally past the front wing bases in the shape of an INVERTED U - Abdominal segments T1 through T4 hair color BLACK - Abdominal segment T5 hair color ALL BLACK, with some specimens showing 2 small white or LIGHT COLORED SPOTS on either side of the segment - Very rare and hard to find specimen, thought to be endangered or possibly extinct, with the last documented specimen found in 2006, note that we only had 1 specimen of B. franklini to compare to and used information from http://www.xerces.org/franklins-bumble-bee/ for additional information. (1)
 B. occidentalis - Facial hair color COMPLETELY DARK, both above antennae and above ocelli, with no specimens showing light or yellow hairs - Thorax hair color on scutum all YELLOW only up to the base of the front wings with BLACK hair starting at the wing bases and extending basally, with some specimens showing only a band of dark hair at the wing bases with the rest of the scutum yellow - Abdominal segments T1 through T4 hair color HIGHLY VARIABLE ranging from light to black hairs on segments, but with no single specimen showing all black hair on T1, T2, T3, and T4 at the same time - Abdominal segment T5 hair color varies between light yellows and WHITE (1)
Females, parasitic vs non-parasitic queens and workers
 Non-Parasitic, common species, outer part of tibia largely hairless, flat, or concave, and rimmed by long hairs (42)
 Parasitic, rare to uncommon species, hairs on outer face of tibia uniform in density and length throughout, tibia uniformly convex (2)
Head, color of hairs just behind ocelli
 Both light and dark hairs (57)
 Light (49)
 Black (26)
Head, long hairs located just above antennae - Note that there is usually a fuzz of shorter, highly branched hairs that are often yellow, at the base of the longer hairs, these short hairs should be ignored
 Both light and dark hairs (57)
 Light (44)
 Black (32)
Head, malar space, the space between mid-point of attachment of mandible and very bottom of eye compared to width of base of mandible
 Clearly longer (45)
 Roughly equal (42)
 Clearly shorter (28)
Head, ocelli, position relative to imaginary line across tops of eyes
 About right on the line (60)
 Distinctly below (18)
Male, B. appositus vs. B. bifarius vs. B. centralis
 B. appositus - Head, malar space, space between mandible and bottom of eye compared to width of base of mandible DISTINCTLY LONG - Hair color above antennae all yellow but usually with A FEW BLACK HAIRS MIXED IN - Thorax, hair color on rear half of scutum a DISTINCT BAND OF BLACK - Scutellum hair color GOLD or ORANGE - Hind leg, projecting hairs on rear edge of tibia BLACK - Abdomen, segment T2 through T6 hair color GOLDEN never with any black hairs mixed in (1)
 B. centralis - Head, malar space, space between mandible and bottom of eye compared to width of base of mandible DISTINCTLY LONG - Hair color above antennae ALL YELLOW with no black hairs present - Thorax, hair color on rear half of scutum usually has BLACK HAIRS MIXED IN without a distinct band of black - Scutellum hair color YELLOW or GOLD - Hind leg, projecting hairs on rear edge of tibia YELLOW - Abdomen, segment T3, T4, and T5 hair color can be GOLD or ORANGE - T6 hair color DARK BROWN or BLACK (1)
Male, B. appositus vs. B. fervidus vs. B. huntii
 B. appositus - Head, hair color above antennae YELLOW but usually with a FEW BLACK HAIRS MIXED IN of the same length - Hair color behind ocelli YELLOW - Hind leg, long projecting hairs on rear edge of tibia BLACK - Abdomen, segment T2 through T6 hair color GOLD (1)
 B. fervidus - Head, hair color above antennae LONG BLACK HAIRS MIXED WITH SHORT YELLOW hairs - Hair color behind ocelli BLACK - Hind leg, long projecting hairs on rear edge of tibia BLACK - Abdomen, segment T2 through T5 hair color GOLD - T6 hair color GOLD or BLACK (1)
 B. huntii - Head, hair color above antennae YELLOW - Hair color behind ocelli YELLOW - Hind leg, long projecting hairs on rear edge of tibia YELLOW - Abdomen, segment T2 through T4 hair color GOLD or ORANGE - T6 hair color BLACK (1)
Male, B. appositus vs. B. sonorus vs. B. vandykei
 B. appositus - Head, hair color above antennae YELLOW with a few black hairs mixed in - Thorax, hair color on rear half of scutum a distinct BAND OF BLACK - Hind leg, long projecting hairs on rear edge of tibia BLACK colored - Abdomen, segment T5 hair color GOLD (1)
 B. sonorus - Head, hair color above antennae mostly BLACK LONG HAIRS with some shorter YELLOW HAIRS MIXED IN - Thorax, hair color on rear half of scutum a distinct BAND OF BLACK - Hind leg, long projecting hairs on rear edge of tibia BLACK colored - Abdomen, segment T5 hair color BLACK (1)
 B. vandykei - Head, hair color above antennae YELLOW - Thorax, hair color on rear half of scutum YELLOW with no distinct band of black hairs - Hind leg, long projecting hairs on rear edge of tibia YELLOW colored - Abdomen, segment T5 hair color GOLD (1)
Male, B. bifarius vs. B. huntii vs. B. vandykei
 B. huntii - Head, malar space, space between mandible and bottom of eye compared to width of base of mandible about equal to LONG - Thorax, hair color on rear half of scutum a DISTINCT BAND OF BLACK hairs - Abdomen, segment T3 hair color usually BRIGHT ORANGE, but sometimes yellow (1)
 B. vandykei - Head, malar space, space between mandible and bottom of eye compared to width of base of mandible about equal to LONG - Thorax, hair color on rear half of scutum YELLOW, with no black hairs present - Abdomen, segment T3 hair color YELLOW, not bright orange (1)
Male, B. bifarius vs. B. melanopygus vs. B. mixtus
 B. melanopygus - Head, facial hair color YELLOW and BLACK mix - Thorax, scutum hair color front half YELLOW AND BLACK MIX or primarily yellow, rear half BLACK - Scutellum hair color YELLOW, sometimes with a strip of black or no hair down the center - Leg, hind tibia hair color BLACK, although it can appear yellow in faded museum specimens - Abdomen, T2 and T3 segment hair color BRIGHT ORANGE to reddish - T4 hair color usually a mix of YELLOW and BLACK or primarily yellow - T5 and T6 hair color BLACK or primarily black (1)
 B. mixtus - Head, facial hair color YELLOW - Thorax, scutum hair color front half YELLOW occasionally with a few black hairs mixed in, rear half yellow and black MIX or all BLACK -Scutellum ALL YELLOW - Leg, hind tibia hair color YELLOW - Abdomen, T2 segment hair color YELLOW to orange - T3 hair color ALL BLACK, primarily black mixed with some yellow, or black on front half of segment and yellow on the rear half - T4 through T6 hair color YELLOW to ORANGE (1)
Male, B. caliginosus vs. B. vosnesenskii
 B. caliginosus - Thorax, scutellum hair color black with a FEW YELLOW hairs mixed in towards the rear, may need to look closely - Leg, middle or hind femur hair color YELLOW on the underside - Abdomen, T5 segment hair color black with a couple YELLOW hairs on each side of the segment and along the rear rim in a very thin border, yellow rim only one or two hairs thick - Difficult to tell apart from B. vosnesenskii and needs very close inspection of hair color (1)
 B. vosnesenskii - Thorax, scutellum hair color COMPLETELY BLACK - Leg, middle and hind femur hair color ALL BLACK - Abdomen, T5 segment hair color black with a small to large PATCH of YELLOW on each side, sometimes with only a small patch of black hairs in the center of the segment - Difficult to tell apart from B. caliginosus and needs very close inspection of hair color (1)
Male, B. centralis vs. B. fervidus vs. vandykei
 B. centralis -Thorax, hair color of rear half of scutum YELLOW, sometimes with a few dark hairs mixed in - Abdomen, segment T5 hair color usually BLACK, but sometimes bright orange - Found from the Rocky Mountains WEST (1)
 B. fervidus - Thorax, hair color of rear half of scutum a DISTINCT BAND OF BLACK - Abdomen, segment T5 hair color GOLD - Found throughout North America (1)
 B. vandykei - Thorax, hair color of rear half of scutum YELLOW, with no black hairs present - Abdomen, segment T5 hair color YELLOW or GOLD - Only found in California and perimeter areas of neighboring states (1)
Male, B. centralis vs. B. flavifrons
 B. centralis - Abdomen, T3 and T4 segment hair color ORANGE often bright orange - T5 hair color BLACK or often ORANGE (1)
 B. flavifrons - Abdomen, T3 and T4 segment hair color YELLOW, with T4 sometime half yellow and half black - T5 hair color always BLACK (1)
Male, B. centralis vs. B. sonorus
 B. centralis - Head, facial hair color YELLOW - Thorax, hair color beneath base of front wing YELLOW - Hind leg, long projecting hairs on rear edge of tibia YELLOW colored (1)
 B. sonorus - Head, facial hair color primarily LONG BLACK HAIRS mixed with some SHORT YELLOW hairs - Thorax, hair color beneath base of front wing BLACK - Hind leg, long projecting hairs on rear edge of tibia BLACK colored (1)
Male, B. crotchii vs. B. griseocollis vs. B. rufocinctus
 B. crotchii - Head, hair color on the side of the antennae all YELLOW with a very few black hairs mixed in - Thorax, color of hair below base of front wing YELLOW with BLACK PATCHES intermixed - Scutum, rear half hair color a distinct BAND OF BLACK - Abdomen, T2 segment hair color all YELLOW or yellow with black hairs along the center of the rear rim - Primarily found in western North America (1)
 B. griseocollis - Head, hair color on the sides of the antennae all YELLOW with a very few black hairs mixed in - Thorax, color of hair below base of front wing ALL YELLOW - Scutum, rear half hair color all YELLOW - Abdomen, T2 segment hair color BLACK with a YELLOW PATCH, sometimes orangish red, in the center of the segment, or yellow hairs along the front rim of the segment - Found throughout North America (1)
 B. rufocinctus - Head, hair color on the sides of the antennae BLACK - Thorax, color of hair below base of front wing ALL YELLOW - Scutum, rear half hair color all YELLOW - Abdomen, T2 segment hair color ALL YELLOW - Found throughout North America (1)
Male, B. fervidus vs. B. huntii vs. B. sonorus
 B. fervidus - Head, facial hair color mostly LONG BLACK HAIRS mixed with some SHORT YELLOW HAIRS - Thorax, hair color below base of front wing BLACK - Hind leg, long projecting hairs on rear edge of tibia BLACK colored - Abdomen, segment T2 through T4 hair color YELLOW or GOLD never bright orange - T5 hair color YELLOW or primarily yellow (1)
 B. huntii - Head, facial hair color YELLOW - Thorax, hair color below base of front wing YELLOW - Hind leg, long projecting hairs on rear edge of tibia YELLOW colored - Abdomen, segment T2 through T4 hair color YELLOW or BRIGHT ORANGE -T5 hair color YELLOW (1)
 B. sonorus - Head, facial hair color mostly LONG BLACK HAIRS mixed with some SHORT YELLOW HAIRS - Thorax, hair color below base of front wing BLACK - Hind leg, long projecting hairs on rear edge of tibia BLACK colored - Abdomen, segment T2 through T4 hair color YELLOW or GOLD never bright orange - T5 hair color BLACK (1)
Male, B. fervidus vs. B. sitkensis
 B. fervidus - Head, facial hair color LONGER BLACK hairs mixed with SHORTER LIGHT hairs - Thorax, scutum rear half hair color BAND OF BLACK - Leg, hind tibia hair color BLACK and short (1)
 B. sitkensis - Head, facial hair color ALL LIGHT - Thorax, scutum rear half hair color primarily YELLOW with some BLACK MIXED IN - Leg, hind tibia hair color YELLOW and long (1)
Male, B. flavifrons vs. B. sitkensis vs. B. vandykei
 B. flavifrons - 3 different forms - Form 1 - Thorax, scutum rear half hair color mostly or all BLACK - Abdomen, T1 and T2 hair color YELLOW - T3 through T6 hair color BLACK - Form 2 - Thorax, scutum rear half hair color mostly or all BLACK - Abdomen, T1 and T2 hair color YELLOW to ORANGE - T3 and T4 hair color ORANGE - T5 and T6 hair color BLACK - Form 3 - Thorax, scutum rear half hair color YELLOW - Abdomen, T1 and T2 hair color YELLOW - T3 and T4 hair color BLACK ON TOP half and YELLOW ON BOTTOM half - T5 and T6 BLACK (1)
 B. sitkensis - Thorax, scutum rear half hair color all BLACK or mostly black with some yellow hairs mixed in - Abdomen, T1 and T2 hair color YELLOW - T3 and T4 color BLACK ON TOP half and YELLOW ON BOTTOM half, in some cases, T4 may only have a few yellow hairs on the rear rim of the segment - T5 hair color BLACK - T6 hair color YELLOW (1)
 B. vandykei - Thorax, scutum rear half hair color YELLOW - Abdomen, T1 through T6 hair color YELLOW (1)
Male, B. flavifrons vs. B. sonorus
 B. flavifrons - Head, facial hair color ALL YELLOW - Thorax, hair color below base of front wing ALL YELLOW - Leg, tibia hair color YELLOW (1)
 B. sonorus - Head, facial hair color ALL BLACK - Thorax, hair color below base of front wing ALL BLACK - Leg, tibia hair color BLACK (1)
Male, B. huntii vs. B. melanopygus
 B. huntii - Thorax, scutum hair color front half ALL YELLOW or gold - Leg, hind tibia hair color YELLOW - Abdomen, T5 segment hair color YELLOW often with a patch of black in the center, sometimes yellow and black mix (1)
 B. melanopygus - Thorax, scutum hair color front half YELLOW AND BLACK MIX or primarily yellow with a few black hairs mixed in - Leg, hind tibia hair color BLACK, although it can appear yellow in some faded museum specimens - Abdomen, T5 segment hair color BLACK or mostly black (1)
Male, B. insularis vs. B. suckleyi
 B. insularis - Head, hair color above antennae usually tufts of YELLOW BORDERED BY BLACK - Specimens where hair color above antennae is all black are indistinguishable from B. suckleyi - Ranges throughout the United States and Canada (1)
 B. suckleyi - Head, hair color above antennae ALL BLACK - Indistinguishable from B. insularis specimens that have all black hair above antennae - Found primarily from the Rocky Mountains WEST (1)
Male, B. melanopygus vs. B. sonorus vs. B. vandykei
 B. melanopygus - Head, hair color above ocelli primarily YELLOW sometimes with some black hairs mixed in - Thorax, scutum hair color front half YELLOW AND BLACK MIX or primarily yellow with a few black hairs mixed in, rear half primarily BLACK mixed with some yellow hairs - Below base of front wing, hair color ALL YELLOW - Leg, hind tibia hair color BLACK, and long, hairs can appear yellow in some older faded museum specimens - Abdomen, T2 and T3 segment hair color BRIGHT ORANGE to reddish (1)
 B. sonorus - Head, hair color above ocelli primarily BLACK sometimes with some yellow hairs mixed in - Thorax, scutum hair color front half YELLOW or golden, rear half ALL BLACK - Below base of front wing, hair color ALL BLACK or at least partially black, older museum specimens may be faded and hard to tell - Leg, hind tibia hair color BLACK and short - Abdomen, T2 and T3 segment hair color YELLOW (1)
 B. vandykei - Head, hair color above ocelli ALL YELLOW - Thorax, scutum hair color front half ALL YELLOW, back half ALL YELLOW occasionally with a couple black hairs mixed in - Below base of front wing, hair color ALL YELLOW - Leg, hind tibia hair color YELLOW - Abdomen, T2 and T3 hair color YELLOW (1)
Male, B. melanopygus vs. B. sylvicola
 B. melanopygus - Head, hair color above antennae YELLOW sometimes with a few black hairs mixed in - Thorax, scutum hair color front half YELLOW AND BLACK MIX or primarily yellow with a few black hairs mixed in - Leg, hind tibia hair color BLACK, although it can appear yellow in some faded museum specimens (1)
 B. sylvicola - Head, hair color above antennae mostly BLACK usually with some yellow hairs mixed in, very rarely primarily yellow - Thorax, scutum hair color front half ALL YELLOW or gold - Leg, hind tibia hair color YELLOW (1)
Male, B. mixtus vs. B. occidentalis vs. B. perplexus
 B. mixtus - Thorax, rear half of scutum hair color primarily YELLOW with few black hairs mixed in - Leg, hind tibia hair color YELLOW - Abdomen, segment T1 hair color YELLOW (1)
 B. occidentalis - Thorax, rear half of scutum hair color all or almost ALL BLACK - Leg, hind tibia hair color YELLOW - Abdomen, segment T1 hair color BLACK (1)
Male, B. mixtus vs. B. sitkensis vs. B. vagans
 B. mixtus - Leg, hind tibia hair color YELLOW - Abdomen, segment T3 hair color HIGHLY VARIABLE, encompassing the states of both B. sitkensis and B. vagans - T5 and T6 hair color primarily YELLOW or ORANGISH (1)
 B. sitkensis - Leg, hind tibia hair color YELLOW - Abdomen, segment T3 hair color BLACK on the front half and YELLOW along the rear rim - T5 hair color primarily BLACK - T6 hair color YELLOW to VERY SLIGHTLY ORANGISH (1)
Male, B. mixtus vs. B. vandykei
 B. mixtus - Abdomen, T3 segment hair color BLACK or sometime a mix of black and yellow - T4 and T5 hair color ORANGE, sometimes appears yellow in older faded museum specimens - Found throughout western North America (1)
 B. vandykei - Abdomen, T3 and T4 segment hair color YELLOW - T5 hair color YELLOW or sometimes black - Only found in California and its neighboring states (1)
Male, B. occidentalis vs. B. sonorus vs. B. vandykei
 B. occidentalis - Head, hair color above ocelli primarily YELLOW - Thorax, scutum hair color rear half all BLACK - Below base of front wing, hair color ALL BLACK or at least partially black, older museum specimens may be faded and hard to tell - Leg, hind tibia hair color YELLOW with some darker hairs mixed in and LONG (1)
 B. sonorus - Head, hair color above ocelli primarily BLACK sometimes with some yellow hairs mixed in - Thorax, scutum hair color rear half ALL BLACK - Below base of front wing, hair color ALL BLACK or at least partially black, older museum specimens may be faded and hard to tell - Leg, hind tibia hair color BLACK and SHORT (1)
 B. vandykei - Head, hair color above ocelli ALL YELLOW - Thorax, scutum hair color rear half ALL YELLOW occasionally with a couple black hairs mixed in - Below base of front wing, hair color ALL YELLOW - Leg, hind tibia hair color YELLOW and LONG (1)
Male, B. occidentalis vs. B. sylvicola
 B. occidentalis - Thorax, below base of front wing, hair color all or mostly BLACK, occasionally just a little bit of black closer to the rear - Abdomen, T1 segment hair color BLACK or almost all black - T2 hair color BLACK, YELLOW, or MIX of black and yellow usually one color in the middle and one on the sides - T2 hair color BLACK, YELLOW, or MIX of black and yellow usually one color in the middle and one on the sides (1)
 B. sylvicola - Thorax, below base of front wing, hair color ALL YELLOW - Abdomen, T1 segment hair color YELLOW - T2 and T3 hair color BRIGHT ORANGE or sometimes lighter in older specimens (1)
Male, B. sylvicola vs. B. sonorus vs. B. vandykei
 B. sonorus - Head, hair color above ocelli primarily BLACK sometimes with some yellow hairs mixed in - Thorax, scutum hair color front half YELLOW or golden, rear half ALL BLACK - Below base of front wing, hair color ALL BLACK or at least partially black, older museum specimens may be faded and hard to tell - Leg, hind tibia hair color BLACK and short - Abdomen, T2 and T3 segment hair color YELLOW (1)
 B. sylvicola - Head, hair color above ocelli ALL YELLOW - Thorax, scutum hair color front half ALL YELLOW, rear half ALL BLACK - Below base of front wing, hair color ALL YELLOW - Leg, hind tibia hair color YELLOW - Abdomen, T2 and T3 hair color BRIGHT ORANGE, older faded museum specimens may appear to be yellow (1)
 B. vandykei - Head, hair color above ocelli ALL YELLOW - Thorax, scutum hair color front half ALL YELLOW, back half ALL YELLOW occasionally with a couple black hairs mixed in - Below base of front wing, hair color ALL YELLOW - Leg, hind tibia hair color YELLOW - Abdomen, T2 and T3 hair color YELLOW (1)
Male, parasitic vs non-parasitic
 Non-parasitic, common, in most but not all species the outer surface of the hind tibia has longer hairs along the front and rear edges with a region of bare or much shorter and less dense hairs in the center, in cross-section, this face also often flattened or deformed slightly from bi-lateral symmetry, the thickest portion usually shifted towards the front edge, fervidus and pensylvanicus are the main exceptions, having short uniform black hairs throughout, but tibia is thicker towards the front edge and underside of segment exceptionally flat, ocelli can be below the level of the eyes or if at the level of the eyes the lateral ocelli are equally distant between the eye and rear head margin or closer to the rear margin, warning, a few species do have ocelli clearly closer to the eye (21)
 Parasitic, relatively rare to uncommon, outer surface of hind tibia uniformly hairy in density and hair length, hairs may be long or short, shape in cross-section is symmetrical, gently rounded with thickest portion running along center or only very slightly towards the front edge of the leg, ocelli always at level with the tops of the eyes, lateral ocelli always much nearer to eye than to rear margin of head (2)
PSITHYRUS ONLY - Females, Abdomen, T6, hair color - CAREFUL, hair may have been rubbed off
 Longer, black hairs present at least mediobasally, not counting any hairs that may be present in the dense lateral patches if present (1)
 No longer black hairs present on T6 (1)
PSITHYRUS ONLY - Females, Abdomen, T6, lateral hair patches - CAREFUL, hair may have been rubbed off
 Hair relatively uniformly present throughout T6, if of varying density then without seemingly elevated lateral hair patches running along the edges of T6 (1)
 Lateral hair patches present, hair density SIGNIFICANTLY higher along the lateral sides of the segment such that the surface integument is completely or nearly completely obscured along the sides, the patches appearing to rise off the surface in the form of hairy ridges (1)
Queen vs Worker - General guidance - It is often difficult to tell queens from workers without a direct comparison between the two
 Queen, usually much larger, active and most abundant earlier in spring (21)
 Worker, smaller and often more variable in size, active from mid-spring into summer (20)
SUBGENUS PSITHYRUS ONLY - Male, head, antennal length of first three flagellomeres
 Third flagellar segment normal, about equal in length to the first flagellomere (1)
 Third flagellar segment very long, equal in length to the first and second flagellomeres combined or nearly so (1)
Sex, antennal segment number
 Female, 12 (44)
 Male, 13 (23)
State or province where bee was collected
 CA (67)
 OR (61)
 WA (58)
 British Columbia (52)
 ID (49)
 MT (49)
 UT (49)
 NV (47)
 Alberta (46)
 CO (46)
 WY (46)
 AZ (41)
 NM (38)
 SD (34)
 Saskatchewan (31)
 Arctic tundra or taiga (29)
 NE (28)
 AK (26)
 ND (25)
 Quebec (23)
 MN (22)
 Manitoba (21)
 Ontario (21)
 Yukon (21)
 IA (20)
 WI (19)
 Northwest Territories (14)
 Newfoundland and Labrador (12)
 CT (11)
 IL (11)
 IN (11)
 MA (11)
 ME (11)
 MI (11)
 NH (11)
 NY (11)
 PA (11)
 VT (11)
 KS (9)
 WV (9)
 GA (8)
 KY (8)
 MD (8)
 NC (8)
 NJ (8)
 New Brunswick (8)
 Nova Scotia (8)
 OH (8)
 Prince Edward Island (8)
 RI (8)
 SC (8)
 TN (8)
 VA (8)
 AL (6)
 AR (6)
 DC (6)
 DE (6)
 MO (6)
 MS (6)
 TX (6)
 FL (3)
 LA (3)
Subgenus
 Pyrobombus (30)
 Cullumanobombus (12)
 Thoracobombus (9)
 Bombus (6)
 Psithyrus (4)
 Bombias (3)
 Subterraneobombus (3)
Thorax, below base of front wing, hair color
 Light (53)
 Light and dark hairs mixed or in patches (41)
 Black, though usually with a small amount of yellow hair at the very top, covering not more than about 1/4 of segment (35)
Thorax, scutellum, color of hairs
 Light (50)
 Light and dark hairs mixed or in patches (43)
 Black (30)
Thorax, scutum, color of hairs in front third
 Light (60)
 Both light and dark hairs mixed (28)
Thorax, scutum, color of hairs on REAR HALF of plate
 Black (55)
 Light and dark hairs mixed or in patches (55)
 Light (22)