A photographic key based on color patterns for bumble bees in Washington state

This key may not work as well in other parts of the country

Some interpretive notes:

  • Red is often short-hand for orange, in descriptions
  • Light colored area may be either yellow or white on a given individual, e.g., Two form bumble bee.
  • Golden refers to a deep rich yellow, e.g., Nevada bumble bee
  • ID means the key has predicted a species based on previous questions
Step        DescriptionGo to #  Comments or link to diagram or species
Female vs Cuckoo/male 
1Corbiculum / pollen basket present5 Corbiculum defined
1’Rearmost leg hairy/rounded2 No pollen basket, see example
Cuckoo female vs all males 
2 (1)Heavy bodied cuckoo female3 What are cuckoo bumble bees?
2’Male, any speciesIDNo key provided at this time
Separating cuckoo queens 
3 (2)T4 with black notchIDIndiscriminate cuckoo bumble, B. insularis
3’T4 w/out black notch4 
4 (3’)T4 yellow, T5 all black, occiput with yellow hairsIDFernald cuckoo bumble bee, B. flavidus
4’T5 with some yellow, black notch, occiput with predominately black hairsIDSuckley cuckoo bumble, B. suckleyi
(very rare)
Starting all non-cuckoos 
5 (1)White on either scutum (thorax front of wings) or T4+T56bumbles showing white
5’No white areas as described above7 
Bumbles showing white 
6 (5)White scutum, golden abdomenIDWhite-shouldered bumble, B. appositus
6’Scutum golden, T4 and T5 whiteIDWestern bumble bee,
B. occidentalis
Bumbles showing yellow 
7 (5’)Bumble bee predominately yellow8Bumbles showing yellow

males of several species may be yellow (e.g., flavifron, mixtus) check rearmost leg for pollen basket
7’May show yellow but other colors also, may be striped9

Separating Yellow bumble from California bumble 
8 (7)T1-T4 yellow, T5,T6 blackYellow bumble bee,
B. fervidus
8’Black wing band, T2 and T3 shows some blackCalifornia bumble bee,
B. californicus

Bees showing red on abdomen 
9 (7’)Red on abdomen10Red on abdomen
9’No red on abdomen21 
Separating Reds into 2 subgroups 
10 (9)Red on middle of abdomen11Example of Red on Middle
10’Red at hind end of abdomen18Example of Red at hind end
Red on middle of abdomen group 
11 (10)Scutum yellow, T1 and T2 yellow, T3 and T4 red/OJ, T5 blackIDCentral bumble bee,
B. centralis
11’Not as above12 
12 (11’)Scutum cloudy, T1 and T2 yellow, T3 and T4 OJ/black, T5 blackIDYellow head bumble,
B flavifrons
red color morph
12’Not as above13 
13 (12’)T2 and T3 red/orange14 
13’T2 or T3 show red/orange17 
14 (13)Scutum cloudy15 
14’Scutum yellow, no black hairs16 
15 (14)Black inverted triangle on scutellum, range associated with San Juan Islands, often black notch on T2IDVancouver bumble bee, B. vancouverensis
15’T1 yellow, T4 black w white hairs in lineIDBlack tail bumble bee,
B. melanopygus
16 (14’)T4 yellow, dry eastern lowlandsIDHunt bumble, B. huntii
16’T4 yellow, high elevations onlyIDForest bumble,
B. sylvicola
17 (13’)Scutum and scutellum both yellow, T2 usually shows at least some yellow
small body size, very short face
IDRed-belted bumble,
B. rufocinctus
17’Scutellum with black inverted triangleIDTwo form bumble,
B. bifarius (red morphs)
Red at hind end of abdomen Group 
18 (10’)Scutum cloudy19 
18’Scutum yellow20 
19 (18)T3 orange sometimes with black, T4 and T5 orange, distinct “red” tailIDFuzzy-horned bumble,
B. mixtus
19’T3 black, T4 and T5 pale orange hairs, subtleIDSitka bumble, B. sitkensis
20 (18’)T3 blackIDFrigid bumble bee,
B. frigidus
20’T3 black and yellowIDHigh country bumble,
B. kirbiellus
red form
No Red on Abdomen 
21 (9’)No red, yes stripes22See examples
21’Hind end of abdomen black26 See examples
Striped bumbles 
22 (21)T1 and T4 white or yellow,
inverted black triangle on scutellum
IDTwo form bumble,
B. bifarius
22’Not as above23 
23 (22’)Face black, scutum and T4 yellowIDCalifornia bumble bee,
B. californicus
23’Face yellow24 
24 (23’)T3 yellowvan Dyke bumble, B. vandykei
24’T3 black25 
25 (24’)Stergites black, hair very evenIDYellow-faced bumble,
B. vosnesenskii
25’Stergites with white hairs, hair shaggyIDObscure bumble bee,
B. caliginosus
Bumbles w black end of abdomen 
26Thorax and T1 thru T4 yellow, T5 black, corbiculum presentIDYellow bumble,
B. fervidus

without pollen basket, may be a male
26’Not as above27 
27 (26’)T2 blackIDCommon eastern bumble, B. impatiens
27’Not as above28 
28 (27’)T3 golden or yellow29 
28’Not as above30 
29 (28’)Black dot between wingsIDNevada bumble,
B. nevadensis
29’No black dot between wingsIDMorrison bumble,
B. morrisoni
(very rare in WA)
30 (28’)Scutum cloudy, T1, T2 yellow, possibly with black notchesIDYellow head bumble bee, B. flavifrons
30’Not as above31 
31 (30’)T1 yellow, T2 with yellow or brown, relatively large bodiedIDBrown-belted bumble,
B. griseocollis
31’T1, T2 yellow, medium to small body sizeIDHalf-black bumble,
B. vagans

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