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Bumble Bees
of the
Eastern
United States
By
Sheila Colla
Leif Richardson
Paul Williams
A product of the USDA Forest Service and the Pollinator Partnership
with funding from the National Fish and Wildlife Foundation
United States
Department of
Agriculture
2 Bumble Bees of the Eastern United States
Executive Editor Larry Stritch, Ph.D., USDA Forest Service
Executive and Managing Editor Laurie Davies Adams, The Pollinator Partnership
Graphic Design and Art Direction Marguerite Meyer
Administration Jennifer Tsang, The Pollinator Partnership
Illustrations Alison Boyd, The Pollinator Partnership
IT Production Support Elizabeth Sellers, National Biological Information
Infrastructure, U.S. Geological Survey
Cover: Male Bombus griseocollis
foraging at cultivated coneflower.
Photo Leif Richardson
Bumble Bees of the Eastern United States 3
Table of Contents
3 Table of Contents
4 Foreword
5 About the Authors
6 Introduction
10 Bee Diagrams
13 Map Methodology
14 Species Guides (color coded)
14-41 Long- or square-cheeked bees with a rounded angle on the midleg
42-61 Short-cheeked bees with a rounded angle on the midleg
62-77 Long-cheeked bees with a sharp angle on the midleg
78-97 Bees with hindleg outer tibial surface convex and uniformly hairy (cuckoo bumble bees)
98 Identification Key
102 Acknowledgements
103 Web and Other Resources
Guide to
Bumble Bees
of the
Eastern
United States
4 Bumble Bees of the Eastern United States
Home bookshelves, school libraries,
nature centers, and museum gift shops
are crowded with dozens of recent field guides to the North American fauna
and flora. Naturalists, young and old, inexperienced and seasoned profes-
sionals, have access to illustrated guides of all types of exciting organisms,
living and dead. But where are the bee identification field guides? More
than 4,000 species of native bees in the United States and Canada are
generally small and lead hidden lives, going mostly unnoticed by almost
everyone. Bigger bees, like bumble bees and carpenter bees, get noticed, as
do the omnipresent brown and black-striped worker honey bees.
Bee identification, including family, genus, and species level, usually in-
volves highly focused specialized training. Bird and butterfly identification
is comparatively easy, which is why there are more bird watchers than bug
watchers and why there are almost no guides available for bee identifica-
tion. The earlier a student of bees adopts professionally recognized scientific
names for bee groups, the easier it becomes.
Typically in bumble bee identification, voucher specimens must be collected
and compared side-by-side with museum specimens. The specimen is
identified using complex professional keys buried in old and hard-to-find
literature. An anonymous quotation captures the complexity of bee identifi-
cation: “taxonomic keys are written by individuals who don’t need them for
others who can’t understand them.”
The Guide to Eastern Bumble Bees is an indispensible new bumble bee
identification resource for the Eastern United States. For the first time,
melittologists (scientists who study bees) Colla, Richardson, and Williams
provide an easy-to-use illustrated and engaging field guide to the most
commonly encountered bumble bees. Each bee species has information
on preferred food plants, nesting biology, and similar species, along with
the seasonal activity patterns for adults at flowers. Closely cropped color
photographs illustrate key color patterns and floral behaviors, while macro
images highlight morphological characteristics and species-level differenc-
es. Additionally, there are detailed dot distribution maps and dichotomous
identification keys for each of the 21 species. The key refers to diagram-
matic “torpedo style” color illustrations of the typical colors for castes of
each species. Much of the information is presented together for the first
time (e.g., dot distribution maps of species ranges).
This new guide is an authoritative tool for learning about our rich and varied
bumble bee fauna. This field guide will enable people to identify, name, and
further explore the colorful and charming bumble bees. This guide encour-
ages exploring nature firsthand from a new perspective. As one young
scientist said, “I really like bumble bees because they are so fuzzy and cute.
It’s hard not to like them.” With the Guide to Eastern Bumble Bees, we not
only admire the Bombus of the East, we can also identify, understand, and
support them as well. Like the canary in the coal mine, several bumble
bees of the eastern region (Bombus terricola, Bombus pensylvanicus, and
especially Bombus affinis) have declined dramatically across their former
wide distributions in the past decade. With the proper identification tools,
students and citizen scientists can help professional entomologists track
their populations and learn why we are losing these essential pollinators.
Stephen Buchmann, Ph.D.
International Coordinator North American Pollinator Protection Campaign
(NAPPC), Co-author of “The Forgotten Pollinators”
Foreword
Bumble Bees of the Eastern United States 5
Sheila R. Colla has studied various
aspects of bumble bee ecology, behavior,
and conservation throughout North
America. She is currently a doctoral
student and recipient of the Natural
Sciences and Engineering Research
Council Alexander Graham Bell Canadian
Graduate Scholarship at York University
under the supervision of Dr. Laurence
Packer in Toronto, Ontario, Canada. Her
dissertation examines changes in bumble
bee communities over the past century
and looks into some of the causes for
observed declines. In addition, she is a
member of the North American Pollinator
Protection Campaign and her research
has been featured in The Washington
Post, Canadian Gardening, The Toronto
Star, BioScience, CBC’s Quirks and
Quarks, and The Daily Planet for
Discovery Channel Canada.
Email: scolla@yorku.ca
Website: www.savethebumblebees.com
Leif Richardson is a graduate student
at Dartmouth College, where he is doing
dissertation research on plants and
their pollinators. He holds a master’s
degree from the University of Arizona’s
Department of Ecology and Evolutionary
Biology and worked for many years as an
ecologist with the Vermont Department of
Fish and Wildlife’s Nongame and Natural
Heritage Program. He is documenting the
distribution and decline of bumble bees
in New England and is involved in efforts
to conserve bumble bee populations in
Eastern North America.
Email: leif.l.richardson@dartmouth.edu
Phone: 802-225-6353
Paul Williams studied the distribution
and decline in British bumble bees for a
Ph.D. at Cambridge (UK) in 1985. Since
then, he has continued to work on this
as a research entomologist at the Natural
History Museum, London, UK, but is
looking increasingly at bumble bee
ecology and systematics worldwide, with
field work especially in North America,
the Himalaya, and China. Larger
taxonomic publications have included
faunal revisions of the bumble bees
of Kashmir and more recently on the
bumble bees of Sichuan, on a checklist
of bumble bee species of the world, and
on a series of papers on bumble bee
phylogeny and subgenera.
Overview: www.nhm.ac.uk/bombus
Publications on bumble bees: www.nhm.
ac.uk/bombus/publications.html
About the Authors
Authors are listed in alphabetical order. Each contributed equally.
6 Bumble Bees of the Eastern United States
The genus Bombus (bumble bee) includes approximately
250 species found primarily in temperate regions of
North America, Central America, South America, Europe,
and Asia. They are absent from Australia, lowland India,
and from most of Africa. In the United States, in States
whose boundaries are fully east of the 100th meridian,
there are a total of 21 species.
The common and easily recognized bumble bees are large
and furry corbiculate (i.e., they have smooth areas on
the hindlegs surrounded by stiff bristles for transporting
pollen) bees with no jugal lobe to the hindwing. All
species are eusocial except for members of the
subgenus Psithyrus, which are social parasites that invade
host bumble bee nests to produce offspring.
Introduction Bumble Bees
of the
Eastern
United States
Bumble bee taxonomy
and biogeography
Phylum Arthropoda,
Class Insecta,
Subclass Pterygota,
Order Hymenoptera,
Suborder Apocrita,
Infraorder Aculeata,
Superfamily Apoidea,
Family Apidae,
Subfamily Apinae,
Genus Bombus
Bumble Bees of the Eastern United States 7
Natural History
Bumble bees have the rare physiological capability
(among insects) to choose to thermoregulate. They
are able to generate heat in their thoracic muscles, by
shivering, to reach the required minimum temperature
for flight (approx. 30°C). Given that bumble bees fly in
the spring and fall in temperate regions, this internal
temperature can be well above ambient temperature.
Bumble bees rely entirely on flowering plants for food.
Adults feed primarily on nectar for energy to fuel flight,
but feed their larvae primarily on pollen to provide protein
for growth. Bumble bees are considered to be generalist
foragers. Because of the length of their colony cycles,
bumble bees usually need to feed from a variety of plant
species, including native wildflowers, crop plants, and
introduced species. As can be seen in the following
species pages, there are differences between species in
timing of emergence, length of colony cycle, foraging
behavior, and habitat selection.
The length of the bumble bee’s tongue governs its
food-plant choices, with bees preferring flowers with a
similar depth to their own tongue length, as this tends
to maximize the rate at which they can gather nectar.
Tongue length varies with body size within species, but
also varies among species. Therefore different bumble
bee species with different tongue lengths tend to visit
different food-plant species, resulting in some partitioning
of food-plant usage among bumble bee species. This may
have the effect of reducing competition between bumble
bee species in a community.
The Colony Cycle
Bumble bees are eusocial organisms with annual colonies
in North America (i.e., one year = one generation). This
means bumble bees live in colonies comprised of several
different ‘castes’ who divide the reproductive, foraging,
8 Bumble Bees of the Eastern United States
defense, and other tasks necessary to their survival. Reproductive
females, or ‘queens,’ live with their male and female offspring,
and all employ an array of physiological and behavioral
adaptations for communication. Mated queens emerge from
hibernation in the spring after overwintering and begin feeding.
Spring queens search for a suitable nest site where they then
begin their colonies. Eggs hatch after approximately 4 days and
the small larvae begin to feed on pollen mixed with nectar. The
larval stage of bumble bees has four instars. After almost 2 weeks
of development, the larvae spin cocoons and pupate. Pupae
develop for another 2 weeks before emerging as full-sized adults.
In total, development takes approximately 5 weeks but this varies
with temperature and food supply. First, female workers emerge
and begin foraging for the colony and feeding the brood. As
the summer progresses, the colony reaches maximum worker
production and begins producing males and potential queens.
These reproductive individuals leave the nest and mate. After
mating, young queens enter diapause and overwinter. The males
and the rest of the colony die with the onset of cold weather in
late fall.
Bumble bee species vary according to how they store pollen and
feed developing larvae. ‘Pollen storers’ accumulate pollen for later
use, often re-using vacated cocoons for this (e.g., B. terricola).
The queen and workers feed each larva individually, opening their
brood cells to regurgitate a mixture of pollen and nectar for them.
By contrast, ‘pocket makers’ place pollen directly in a wax pocket
on the side of a group of larval cells (e.g., B. fervidus). The larvae
of these species all feed from the same pocket, which sometimes
leads to greater size differences in adult bees of the same caste.
Bumble Bees of the Eastern United States 9
Bumble bee species belonging to the subgenus Psithyrus
are an exception as they do not produce a worker caste,
but are social parasites. Females usurp colonies of other
species and reproduce using the host species’ resources. In
the eastern fauna, the parasitic species are: B. ashtoni, B.
citrinus, B. fernaldae, B. insularis, B. variabilis.
Importance in
Natural Ecosystems
and Agriculture
Bumble bees are extremely important pollinators for
agriculture both in the field and in greenhouses. Unlike
honey bees, they are able to forage under cold, rainy, and
cloudy conditions. This makes them excellent pollinators
for a variety of crops in temperate regions. Some crops
that bumble bees can pollinate include tomatoes,
peppers, raspberries, blueberries, chives, cucumbers,
apples, strawberries, alfalfa, blackberries, soybeans,
sunflowers, beans, cherries, apricots, plums, almonds,
nectarines, peaches, rosehips, eggplants, and cranberries.
Bumble bees are also extremely important pollinators of
many flowering plants throughout the native ranges with
which they co-evolved mutualisms where they receive
food in return for providing pollination. Bumble bees are
generalists and have been recorded visiting hundreds of
native plant species. The pollination services bumble
bees provide for native plants are likely very important
for maintaining various ecosystems. In addition, other
animals, like small mammals and birds, rely on the fruits
and seeds of pollinated plants for food.
Bumble Bee Declines
We have evidence that in North America some of
our bumble bee species are declining and a few are
threatened with extinction. One species from Oregon
and California (Franklin’s bumble bee) has recently been
listed by the International Union for Conservation of
Nature (IUCN) as Critically Endangered. Species that
seem most vulnerable are those with smaller climate
tolerances, those at the edge of their climatic niches,
and later emerging species. In North America, members
of the subgenus Bombus sensu strictu (i.e., B. affinis,
B. occidentalis, B. franklini, B. terricola) seem to be
declining at a rapid rate.
Currently, the suspected threats to wild bumble bees are:
habitat loss due to agricultural intensification,
urbanization or pollution,
pesticide use,
pathogen spillover from managed bees,
and climate change.
10 Bumble Bees of the Eastern United States
Bee Body Diagram
thorax
head
foreleg
midleg
hindleg
wings
1
2
3
4
5
6
abdomen
(with
numbered
terga/ “T”
corbiculum/
pollen basket
Bombus ternarius, queen
antenna
Bumble Bees of the Eastern United States 11
Bee Leg Diagram
midleg
femur
tibia
tarsal segments
basitarsus
hindleg
Bombus bimaculatus, male
12 Bumble Bees of the Eastern United States
Bee Face Diagram
ocelli
antenna
clypeus
tongue
cheek (malar space)
mandible
compound eye
supraorbital line
Bombus sandersoni, worker
Bumble Bees of the Eastern United States 13
Map Methodology
The maps produced for this guide provide two sets of information
about the range of each species: points that represent actual bumble
bee collections, and generalized range polygons meant to predict bee
distribution in areas where we lack specimen collection data. Many
institutions and individuals have contributed digitized, georeferenced
specimen data to this effort, and dots on each map represent
collections held by the following:
Sheila Colla, York University
Paul Williams, British Natural History Museum
Leif Richardson, Vermont Department of Fish and Wildlife
Caroline Scully, Antioch University New England
John Ascher, American Museum of Natural History
Ohio State University Hymenoptera Online Database
Illinois Natural History Survey
Yale University, Peabody Museum
University of Connecticut Insect Collections
University of Vermont’s Zadock Thompson Zoology Collection
Canadian National Collection of Insects
Rachael Winfree, Rutgers University
Sam Droege, U.S. Geological Survey, Patuxent Wildlife Research
Center
Michael Arduser, Missouri Department of Conservation
H.E. Milliron (published records from various collections)
Kevin Matteson, Fordham University
Steve Marshall, University of Guelph
Many other insect collections exist that have not been checked for
identification accuracy or digitized. These maps can thus be improved
upon as more data become available.
Maps are at a scale of 1:11,000,000. For each species, a range
polygon (shown in green) was produced by buffering specimen
collection points by 100 kilometers, then merging all buffers together.
We chose this as an arbitrary distance from known locations of
occurrence (i.e., sites where specimens have been collected) because,
in general, we believe that it helps to describe a bumble bee species’
range. Minor changes were made to the resulting layer to connect
adjacent polygons where we thought it appropriate, to smooth some
edges and to improve the presentation of the map. The range polygon
layer was then clipped to the Eastern United States. No range polygon
was made for B. frigidus, because we currently know of just one
specimen of this bee collected in the Eastern United States.
For each species, the specimen collection points from the Eastern
United States are displayed. Data from most sources listed above are
termed ‘Primary Records,’ because we have high confidence in the
determinations (identifications) of those specimens. Data from the
Ohio State University collection are termed ‘Other Records,’ because
we have not verified the determinations of bees in that collection. In a
few cases, we have also displayed points on the maps that represent
photographs of bumble bees, not actual collections. We have only done
this when accurate identification was possible from a photo.
For three species that have undergone precipitous declines in the last
decade—B. affinis, B. terricola, and B. ashtoni—we chose to display
the relatively few collections made after 1997 differently from all
those made previously. This is intended to give the reader a sense of
how much the species’ ranges have shrunk and where they might still
be found.
Range information is shown for all full States east of the 100°
longitude line. Users should bear in mind that most of the bumble
bees found in this area also occur in parts of adjacent Canada and the
Western United States.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Queens
Workers
Males
14 Bumble Bees of the Eastern United States
Bombus impatiens worker foraging on cultivated sunflower
Photo Leif Richardson
Common eastern bumble bee
• Common, possibly expanding range
• Select food plants: Cirsium (Thistles), Eupatorium, Gelsemium,
Solidago (Goldenrods), Pontederia (Pickerel Weeds)
• Tongue length: medium
• Nests underground
• Parasitized by B. citrinus
• Can be confused with B. bimaculatus
Bombus impatiens
Long- or square-cheeked bees with
a rounded angle on the midleg
Bumble Bees of the Eastern United States 15
Lateral image of a female Bombus impatiens.
Photo Sheila Colla
Bombus impatiens
male on aster.
Photo Sheila Colla
Bombus impatiens queen foraging on clover.
Photo Sheila Colla
Bombus impatiens male on oregano.
Photo Leif Richardson
Female Bombus impatiens
face. Photo Sheila Colla
Bombus impatiens continued
16 Bumble Bees of the Eastern United States
Bombus impatienscontinued
Bumble Bees of the Eastern United States 17
Bombus impatiens continued
Females (queens and workers, colors refer to pile or ‘hair’):
• Thorax and T1 predominantly pale yellow, some black
hairs intermixed between the wing bases,
T2 entirely black, tail black.
• Midleg basitarsus with the distal posterior corner
rounded. Cheek as long as broad. Hair of the face
black or with only a few yellow hairs intermixed, black
hairs intermixed diffusely between the wing bases,
hair of T2 always entirely black. Hair short, metasoma
rather long and rectangular.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Queens
Workers
Males
18 Bumble Bees of the Eastern United States
Male Bombus bimaculatus foraging at wild bergamot.
Photo Leif Richardson
Two-spotted bumble bee
• Common
• Select food plants: Cirsium (Thistles),
Hypericum (St. John’s Wort),
Melilotus (Sweet Clovers), Rosa, Solidago (Goldenrods),
Vicia (Vetches)
• Tongue length: medium
• Nests underground and on surface
• Can be confused with B. impatiens, B. griseocollis,
Bombus bimaculatus
Bumble Bees of the Eastern United States 19
Lateral image of a female
Bombus bimaculatus.
Photo Sheila Colla
Bombus bimaculatus queen foraging for
nectar from cultivated azaleas.
Photo Leif Richardson
Bombus bimaculatus worker.
Photo Sheila Colla
Bombus bimaculatus face.
Photo Sheila Colla
Bombus bimaculatuscontinued
20 Bumble Bees of the Eastern United States
Bombus bimaculatuscontinued
Bumble Bees of the Eastern United States 21
Bombus bimaculatuscontinued
Females (queens and workers, colors refer to pile or ‘hair’):
• Thorax and T1 predominantly yellow, a black spot between the
wing bases, T2 usually with a yellow W in the middle, tail black,
hair long.
• Midleg basitarsus with the distal posterior corner rounded.
Cheek slightly longer than broad. Hair of face black or with only
a few yellow hairs intermixed, black hair of the spot between
the wing bases dense and always present, although often
with yellow hairs intermixed, the black hairs only occasionally
forming a band between the wing bases, T2 always
with some yellow hairs present but sometimes with
very few, although if the yellow is extensive then
black hairs are intermixed posteriorly and medially
and the posterior margin of the yellow usually forms a
characteristic W-shape (which may be similar in some
B. griseocollis, although that species usually has some
yellow hairs rather than black anterio-laterally). Hair
long and uneven, metasoma
rather short and globular.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Queens
Workers
Males
22 Bumble Bees of the Eastern United States
Bombus perplexus worker foraging on St. John’s Wort.
Photo Leif Richardson
Confusing bumble bee
• Common
• Select food plants: Hydrangea, Rhododendron, Rubus,
Vaccinium, Lonicera (Honeysuckles), Prunus, Ribes
• Tongue length: medium
• Nests on ground surface and in hollow logs and trees
• Can be confused with B. vagans
Bombus perplexus
Bumble Bees of the Eastern United States 23
Lateral image of a female Bombus perplexus.
Photo Sheila Colla
Bombus perplexus queen.
Photo Leif Richardson
Bombus perplexus male.
Photo Sheila Colla
Female Bombus perplexus face.
Photo Sheila Colla
Bombus perplexus continued
24 Bumble Bees of the Eastern United States
Bombus perplexus continued
Bumble Bees of the Eastern United States 25
Bombus perplexus continued
Females (queens and workers, colors refer to pile or ‘hair’):
• Thorax and T1-2 predominantly brown or yellow, sides
of the thorax often black, tail black or often with some
white hairs.
• Midleg basitarsus with the distal posterior corner
rounded. Cheek slightly longer than broad. Hair of
the face black or with yellow hairs intermixed, only
a very few inconspicuous black hairs in the centre of
the thoracic dorsum between the wing bases, sides
of the thorax often but not always extensively black,
sometimes entirely yellow. Pale hair often brownish
rather than yellow, T5 sometimes with white hair.
Hair long.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Queens
Workers
Males
26 Bumble Bees of the Eastern United States
A worker Bombus vagans visits red clover.
Photo Leif Richardson
Half-black bumble bee
• Common
• Select food plants: Penstemon (Beard-Tongues),
Asclepias (Milkweeds), Asters, Cirsium (Thistles),
Eupatorium, Spirea (Meadowsweet),
• Tongue length: medium
• Nests on ground surface and underground
• Unlike most bumble bees, this species readily forages
in heavily shaded areas within forests
• Can be confused with B. sandersoni, B. perplexus,
B. affinis
• Parasitized by B. citrinus
Bombus vagans
Bumble Bees of the Eastern United States 27
Lateral image of a Bombus vagans female.
Photo Sheila Colla
Female Bombus vagans face.
Photo Sheila Colla
Bombus vagans continued
28 Bumble Bees of the Eastern United States
Bombus vagans continued
Bumble Bees of the Eastern United States 29
Bombus vagans continued
Females (queens and workers, colors refer to pile or ‘hair’):
• Thorax and T1-2 predominantly yellow, a black spot
between the wing bases, sides of the thorax yellow, tail
black, face long.
• Midleg basitarsus with the distal posterior corner
rounded. Cheek slightly longer than broad. Hair of the
face black or with yellow hairs intermixed, the black
thoracic spot between the wing bases may be small and
intermixed with yellow hairs in queens but is larger and
more diffuse in workers, forming a band between the
wing bases, T2 yellow or sometimes with black along the
posterior margin, sometimes intermixed laterally, but not
anteriorly unless the yellow band is very narrow. Hair
long. Body size small, but larger than B. sandersoni.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Workers
Queens
Males
30 Bumble Bees of the Eastern United States
Bombus sandersoni female in Newfoundland, Canada.
Photo Cory Sheffield
Sanderson bumble bee
• Uncommon
• Select food plants: Epilobium, Monarda (Bee Balms),
Penstemon (Beard Tongues), Rubus, Malus (Apples)
• Tongue length: short
• Often confused with B. perplexus and B. vagans.
Difficult to properly identify and this ecology poorly known.
Bombus sandersoni
Bumble Bees of the Eastern United States 31
Lateral image of a Bombus sandersoni female.
Photo Sheila Colla
Lateral image of Bombus sandersoni female, dark morph.
Photo Sheila Colla
Female Bombus sandersoni face.
Photo Sheila Colla
Bombus sandersoni continued
32 Bumble Bees of the Eastern United States
Bombus sandersoni continued
Bumble Bees of the Eastern United States 33
Bombus sandersoni continued
Females (queens and workers, colors
refer to pile or ‘hair’):
• Thorax and T1-2 predominantly
yellow, or with a black spot or band
between the wing bases, sides
of the thorax yellow, tail black or
yellow or occasionally white (not
orange), face round.
• Midleg basitarsus with the distal
posterior corner rounded. Cheek
as long as, or slightly shorter than,
broad. Hair of the face and top of
the head black or with yellow hairs,
corbicular fringes black or with
brownish-orange tips, T2 anterio-
laterally often with a few scattered
black hairs intermixed, T5 black,
brown, yellow, or white, with a few
black hairs intermixed. Hair short
and even, body size small and
smaller than B. vagans.
The phenology for this species is unknown due to few records in the Eastern United States.
34 Bumble Bees of the Eastern United States
Bombus frigidus worker on senecio sp.
Photo Jessica Forrest
Bombus frigidus
• Rare in the United States (recorded only in northern border
States)
• Select food plants: Cirsium (Thistles),
Epilodium Geranium, Mertensia (Bluebells),
Taraxacum officinale (Dandelion), Trifolium (Clovers)
• Tongue length: short
Bombus frigidus
Bumble Bees of the Eastern United States 35
Lateral image of a female Bombus frigidus.
Photo Sheila Colla
Female Bombus frigidus face.
Photo Sheila Colla
Bombus frigidus continued
36 Bumble Bees of the Eastern United States
Bombus frigidus continued
Bumble Bees of the Eastern United States 37
Bombus frigidus continued
Females (queens and workers, colors refer to pile or ‘hair’):
• Thorax and T1-2 predominantly yellow, with a black
band between the wing bases, sides of the thorax
yellow, tail orange (occasionally faded to more
yellowish).
• Midleg basitarsus with the distal posterior corner
rounded. Cheek as long as broad. Hair of the face
black or with some yellow hairs, corbicular fringes
extensively pale orange, T2 anterio-laterally without
scattered black hairs intermixed. Hair long.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Queens
Workers
Males
38 Bumble Bees of the Eastern United States
Bombus ternarius queen visits dandelion.
Photo Leif Richardson
Tri-colored bumble bee
• Common
• Select food plants: Asclepias (Milkweeds), Rubus, Solidago
(Goldenrods), Rhododendron, Vaccinium
• Tongue length: short
• Nests underground
• Can be confused with the red color morph of B. rufocinctus
Bombus ternarius
Bumble Bees of the Eastern United States 39
Lateral image of a Bombus ternarius female.
Photo Sheila Colla
A Bombus ternarius worker
vists cultivated bush pea.
Photo Leif Richardson
Female Bombus ternarius face.
Photo Sheila Colla
Male Bombus ternarius on
Canada goldenrod.
Photo Sheila Dumesh
Bombus ternarius continued
40 Bumble Bees of the Eastern United States
Bombus ternarius continued
Bumble Bees of the Eastern United States 41
Bombus ternarius continued
Females (queens and workers, colors refer to pile or ‘hair’):
• Thorax and T1 predominantly yellow, with a black band
between the wing bases extending posteriorly in the
middle of the scutellum, T2-3 orange, T4 yellow, T5
black, and with face round.
• Midleg basitarsus with the distal posterior corner
rounded. Cheek very slightly shorter than broad.
Hair of face and top of the head black with patches
of yellow, or sometimes with black more extensively
intermixed, especially for workers. Thoracic anterior
band usually yellow without black hairs intermixed
except in some workers, which have the anterior margin
of the black band between the wing bases always
sharply defined. Scutellum with yellow patches entirely
divided by a black, posteriorly directed triangle. T2
red, at most with a few black hairs anterio-medially; T4
yellow; T5 black. Hair short and even.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Queens
Workers
Males
42 Bumble Bees of the Eastern United States
Bombus terricola worker collecting nectar from milkweed.
Photo Leif Richardson
Yellow-banded bumble bee
• Uncommon, possibly declining since the mid-1990s
• Select food plants: Vaccinium, Salix (Willows), Rosa (Roses),
Rubus, Lonicera (Honeysuckles), Solidago (Goldenrods), Asters
• Tongue length: short
• Nests underground
• Nectar robber
• Parasitized by B. ashtoni
• Can be confused with B. pensylvanicus
Bombus terricola
Short-cheeked bees with a
rounded angle on the mid leg
Bumble Bees of the Eastern United States 43
Lateral image of a female Bombus terricola.
Photo Sheila Colla
Bombus terricola male forages on hop clover.
Photo Leif Richardson
Bombus terricola worker visiting purple flowering raspberry.
Photo Leif Richardson
Female Bombus terricola face.
Photo Sheila Colla
Bombus terricola continued
44 Bumble Bees of the Eastern United States
Bombus terricola continued
Bumble Bees of the Eastern United States 45
Bombus terricola continued
Females (queens and workers, colors refer to pile or ‘hair’):
• Thorax with yellow band(s), T1 black, T2-3 yellow, tail
black or yellow, face round.
• Midleg basitarsus with the distal posterior corner
rounded. Cheek length slightly shorter than breadth,
clypeus strongly swollen in the dorsal half, hind
basitarsus with the posterior margin strongly and evenly
arched. Hair of the head black or with a minority of
short pale hairs intermixed. Hair short and even.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Queens
Workers
Males
46 Bumble Bees of the Eastern United States
Bombus affinis worker on spotted knapweed.
Pinery Provincial Park, Ontario.
Photo Sheila Colla
Rusty-patched bumble bee
• Rare after 1997, previously common
• Select food plants: Helianthus (Sunflowers), Asters, Solidago
(Goldenrods), Lonicera (Honeysuckles), Vaccinium,
Prunus, Aesculus
• Tongue length: short
• Nests underground
• Occasional nectar robber
• Parasitized by B. ashtoni
• Can be confused with B. citrinus, B. griseocollis,
B. perplexus, B. vagans
Bombus affinis
Bumble Bees of the Eastern United States 47
Lateral image of a queen Bombus affinis.
Photo Sheila Colla
Lateral image of Bombus affinis worker.
Photo Sheila Colla
Queen Bombus affinis face.
Photo Sheila Colla
Bombus affinis continued
This map, and all subsequent species
maps, provide two sets of information
about the range of each species: points
that represent actual bumble bee
collections, and generalized range polygons
meant to predict bee distribution in areas
where we lack specimen collection data.
Many institutions and individuals have
contributed digitized, georeferenced
specimen data to this effort, and dots
on each map represent many collections
which are listed on page 13 under Map
Methodology along with more information
about the maps for each species.
48 Bumble Bees of the Eastern United States
Bombus affinis continued
Bumble Bees of the Eastern United States 49
Bombus affinis continued
Females (queens and workers, colors refer to pile or ‘hair’):
• Thorax and T1-2 predominantly yellow, or with a
black spot or band between the wing bases, T2 often
distinctly brown in workers, tail black.
• Midleg basitarsus with the distal posterior corner
rounded. Cheek length slightly shorter than breadth,
clypeus strongly swollen in the dorsal half, hind
basitarsus with the posterior margin strongly and evenly
arched. Hair of the face black, hair of the top of the
head black or with only a few yellow hairs intermixed.
Hair of medium length and even.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Queens
Workers
Males
50 Bumble Bees of the Eastern United States
Male Bombus griseocollis foraging at cultivated coneflower.
Photo Leif Richardson
Brown-belted bumble bee
• Common
• Select food plants: Asclepias (Milkweeds), Cirsium (Thistles),
Helianthus (Sunflowers), Solidago (Goldenrods),
Rhus (Sumacs), Lythrum (Loosestrifes)
• Tongue length: medium
• Nests on ground surface
• Can be confused with B. bimaculatus, B. affinis
Bombus griseocollis
Bumble Bees of the Eastern United States 51
Lateral image of a female Bombus griseocollis.
Photo Sheila Colla
Bombus griseocollis workers foraging on prickly pear.
Photo Leif Richardson
A Bombus griseocollis worker captured by a crab spider.
Photo Sheila Colla
Bombus griseocollis face.
Photo Sheila Colla
Bombus griseocollis continued
52 Bumble Bees of the Eastern United States
Bombus griseocollis continued
Bumble Bees of the Eastern United States 53
Bombus griseocollis continued
Females (queens and workers, colors refer to pile or ‘hair’):
• Thorax and T1 predominantly yellow, or with a black
spot between the wing bases; T2 with a yellow or
brown crescent anteriorly, tail black, hair short.
• Midleg basitarsus with the distal posterior corner
rounded. Cheek length distinctly shorter than breadth,
ocelli large. Hair of the face and of the top of the
head black or with only a few yellow hairs intermixed,
black thoracic spot between the wing bases often
very small and inconspicuous but dense. Sometimes
workers have the yellow on T2 extending for three-
quarters of the length of T2 and forming a W-shape
(similar to B. bimaculatus, but with few black hairs
intermixed medially and some yellow hairs intermixed
anterio-laterally). Hair very short and even, the
metasoma rather rectangular and slightly flattened.
54 Bumble Bees of the Eastern United States
Bombus fraternus worker.
Photo Paul Williams
Southern plains bumble bee
• Uncommon
• Select food plants: Hypericum (St. John’s Worts),
Monarda (Bee Balms), Rhus (Sumacs),
Solanum (Nightshades and relatives), Asters,
Cirsium (Thistles)
• Tongue length: short
• Can be confused with B. affinis, B. griseocollis
Bombus fraternus
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Queens
Workers
Males
Bumble Bees of the Eastern United States 55
Lateral image of a female Bombus fraternus.
Photo Sheila Colla
Female Bombus fraternus face.
Photo Sheila Colla
Bombus fraternus continued
56 Bumble Bees of the Eastern United States
Bombus fraternus continued
Bumble Bees of the Eastern United States 57
Bombus fraternus continued
Females (queens and workers, colors refer to pile or ‘hair’):
• Thorax and T1-2 extensively yellow, with a black band
between the wing bases, tail black, hair very short.
• Midleg basitarsus with the distal posterior corner
rounded. Cheek length much shorter than breadth,
ocelli large, hind basitarsus with the posterior margin
almost parallel to the anterior margin. Hair distinctive
for being very short and even, and on the metasoma
decumbent, the metasoma nearly rectangular and
slightly flattened.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Queens
Workers
Males
58 Bumble Bees of the Eastern United States
A black color morph Bombus rufocinctus worker forages at teasel.
Photo Leif Richardson
Red-belted bumble bee
• Common
• Select food plants: Trifolium (Clovers), Melilotus (Sweet Clovers),
Cirsium (Thistles), Solidago (Goldenrods), Eupatorium, Asters
• Tongue length: short
• Nests underground and on ground surface
• Highly variable in coloration and can be confused with
many species
Bombus rufocinctus
Bumble Bees of the Eastern United States 59
Lateral image of a Bombus rufocinctus female, black morph.
Photo Sheila Colla
Bombus rufocintus female.
Photo Leif Richardson
A red color morph Bombus rufocinctus worker forage
at teasel. Photo Leif Richardson
Lateral image of a Bombus rufocinctus female, red morph.
Photo Sheila Colla
Female Bombus rufocintus face.
Photo Sheila Colla
Bombus rufocinctus continued
60 Bumble Bees of the Eastern United States
Bombus rufocinctuscontinued
Bumble Bees of the Eastern United States 61
Bombus rufocinctus continued
Females (queens and workers, colors
refer to pile or ‘hair’):
• Similar to many color patterns
shown by the other Eastern North
American species, but small
bodied, short haired, and with a
short face.
• Midleg basitarsus with the
distal posterior corner rounded.
Cheek length distinctly shorter
than breadth. Many other
combinations of these color
patterns are known, but the hair
of T2 is almost always with at
least a yellow crescent anteriorly
(only rarely very much reduced).
Hind basitarsus with the posterior
margin evenly but not strongly
arched. Hair short and even, body
size small.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Queens
Workers
Males
62 Bumble Bees of the Eastern United States
Bombus fervidus female.
Photo Leif Rchardson
Yellow bumble bee
• Uncommon, possibly in decline
• Select food plants: Lonicera (Honeysuckles),
Cirsium (Thistles), Trifolium (Clovers),
Penstemon (Beard-tongues), Lythrum (Loosestrifes),
Vicia (Vetches), Monarda (Bee balms)
• Tongue length: long
• Nests on ground surface and underground
• Can be confused with B. borealis
• More common in open fields and meadows
Bombus fervidus
Long-cheeked bees with a
sharp angle on the midleg
Bumble Bees of the Eastern United States 63
Lateral image of a Bombus fervidus female.
Photo Sheila Colla
Female Bombus fervidus face.
Photo Sheila Colla
Bombus fervidus continued
64 Bumble Bees of the Eastern United States
Bombus fervidus continued
Bumble Bees of the Eastern United States 65
Bombus fervidus continued
Females (queens and workers, colors refer to pile or ‘hair’):
• Face black, thorax and T1-4 predominantly yellow,
usually with a black band between the wing bases,
sides of the thorax usually yellow, T5 black.
• Midleg basitarsus with the distal posterior corner
sharply pointed. Cheek distinctly longer than broad,
clypeus surface rough with many large punctures.
Hair of the head black or with only a minority of short
pale hairs intermixed, sides of the thorax yellow at
least in the dorsal half (often throughout), black band
between the wing bases may be very narrow (anterior to
posterior) and may have many yellow hairs intermixed.
Hair of medium length and even.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Queens
Workers
Males
66 Bumble Bees of the Eastern United States
Bombus borealis male foraging at red clover.
Photo Leif Richardson
Northern amber bumble bee
• Uncommon
• Select food plants: Vicia (Vetches), Cirsium (Thistles), Asters,
Prunella, Symphytum officinale (Comfrey), Eupatorium
• Tongue length: long
• Nests underground
• Can be confused with B. fervidus
Bombus borealis
Bumble Bees of the Eastern United States 67
Lateral image of a female Bombus borealis.
Photo Sheila Colla
Bombus borealis males
on thistle.
Photo Leif Richardson
Bombus borealis worker foraging at culitivated monkshood.
Photo Leif Richardson
Bombus borealis queen foraging on cow vetch.
Photo Paul Williams
Bombus borealis face.
Photo Sheila Colla
Bombus borealis continued
68 Bumble Bees of the Eastern United States
Bombus borealiscontinued
Bumble Bees of the Eastern United States 69
Bombus borealiscontinued
Females (queens and workers, colors refer to pile or ‘hair’):
• Face yellow, thorax and T1-4 extensively yellow, with a
black band between the wing bases, lower sides of the
thorax usually black, T5 black or yellow.
• Midleg basitarsus with the distal posterior corner
sharply pointed. Cheek distinctly longer than broad,
clypeus surface very smooth and shiny with only a
few very small punctures near the center. Hair of
the face usually gray-yellow and usually paler than
on the rest of the body and only rarely with many
black hairs extensively intermixed, sides of the thorax
predominantly black with yellow only within the dorsal
half. Hair of medium length and even.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Queens
Workers
Males
70 Bumble Bees of the Eastern United States
Bombus pensylvanicus worker foraging on cow vetch.
Photo Paul Williams
American bumble bee
• Uncommon, possibly in decline
• Select food plants: Vicia (Vetches), Lotus corniculata,
Trifolium (Clovers), Solidago (Goldenrods),
Hypericum (St. John’s Wort), Eupatorium
• Tongue length: long
• Nests on ground surface
• Can be confused with B. terricola and B. auricomus
• Parasitized by B. variabilis
Bombus pensylvanicus
Bumble Bees of the Eastern United States 71
Lateral image of a female Bombus pensylvanicus.
Photo Sheila Colla
Female Bombus pensylvanicus face.
Photo Sheila Colla
Bombus pensylvanicus continued
72 Bumble Bees of the Eastern United States
Bombus pensylvanicus continued
Bumble Bees of the Eastern United States 73
Bombus pensylvanicus continued
Females (queens and workers, colors refer to pile or ‘hair’):
• Top of the head black, thorax with yellow band(s), T1
often yellow especially in the middle, T2-3 yellow, tail
black, face long.
• Midleg basitarsus with the distal posterior corner
sharply narrowly produced and spinose, hind basitarsus
with the proximal posterior process long and pointed
(longer than broad). Cheek slightly longer than broad,
clypeus with large punctures except on the mid line.
Hair on the top of the head always black, T1 with
yellow hairs more frequent medially. Hair short and
even.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Queens
Workers
Males
74 Bumble Bees of the Eastern United States
Bombus auricomus worker foraging on a legume.
Photo Paul Williams
Black and gold bumble bee
• Uncommon
• Select food plants: Monarda (Bee balm),
Solanum (Nightshades and relatives), Trifolium (Clovers),
Hypericum (St. John’s Wort), Eupatorium
• Tongue length: long
• Nests underground
• Can be confused with B. pensylvanicus, B. terricola
Bombus auricomus
Bumble Bees of the Eastern United States 75
Lateral image of a female Bombus auricomus.
Photo Sheila Colla
Female Bombus auricomus face.
Photo Sheila Colla
Bombus auricomus continued
76 Bumble Bees of the Eastern United States
Bombus auricomus continued
Bumble Bees of the Eastern United States 77
Bombus auricomus continued
Females (queens and workers, colors refer to pile or ‘hair’):
• Top of the head yellow, thorax with yellow band(s), T1
often yellow especially laterally, T2-3 yellow, tail black,
face long.
• Midleg basitarsus with the distal posterior corner acute
but not narrowly produced, hind basitarsus with the
proximal posterior process broad and blunt (shorter
than broad). Cheek slightly longer than broad, ocelli
large, mandible with anterior keel not reaching the
distal margin, clypeus very evenly covered with small
punctures. Hair on the face black, occasionally with
a few yellow hairs intermixed; top of the head usually
yellow, sometimes with black hairs intermixed but
occasionally predominantly black; T1 with yellow hairs
more frequent laterally. Hair very short and even.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Females
Males
78 Bumble Bees of the Eastern United States
Bombus citrinus male on Woodland Sunflower.
Photo Sheila Colla
Lemon cuckoo bumble bee
• Common
• Select food plants: Asclepias (Milkweeds), Rubus,
Verbena (Vervains), Eupatorium, Trifolium (Clovers),
Solidago (Goldenrods)
• Hosts: B. impatiens and B. vagans
• Can be confused with B. affinis, B. perplexus, B. vagans
Bombus citrinus
Bees with hindleg outer tibial surface convex
and uniformly hairy (cuckoo bumble bees)
Bumble Bees of the Eastern United States 79
Lateral image of a female Bombus citrinus.
Photo Sheila Colla
Female Bombus citrinus.
Photo J. Lucier
Female Bombus citrinus face.
Photo Sheila Colla
Bombus citrinus continued
80 Bumble Bees of the Eastern United States
Bombus citrinus continued
Bumble Bees of the Eastern United States 81
Bombus citrinus continued
Females (no workers, colors refer to pile or ‘hair’):
• Thorax predominantly yellow, including the
lower sides, T4-5 black.
• Hind tibia with the outer surface convex and
densely hairy. Hair of the face black, usually
with only a minority of yellow hairs intermixed;
yellow hair above the base of the antenna rarely
dense. Sides of the thorax entirely yellow;
thoracic dorsum usually without black hair, but
if present, then not forming a band between
the wing bases. T4-5 predominantly black.
Wings light brown, hair on the metasoma short
(but longer on T5 than length of last joint of
hind tarsus) and even, T6 matte with dense
punctures.
Because of the extreme scarcity of this species, natural history and
ecology details are not well known. Photos of this species in the wild
are also scarce.
82 Bumble Bees of the Eastern United States
Variable cuckoo bumble bee
• Extremely rare, possibly extinct
• Select food plants: Asclepias (Milkweeds), Aster,
Cirsium (Thistles), Solidago (Goldenrods), Eupatorium,
Trifolium (Clovers)
• Parasitizes B. pensylvanicus
Bombus variabilis
Female Bombus variabilis.
Photo Sheila Colla
Bumble Bees of the Eastern United States 83
Lateral image of a Bombus variabilis female.
Photo Sheila Colla
Female Bombus variabilis face.
Photo Sheila Colla
Bombus variabilis continued
84 Bumble Bees of the Eastern United States
Bombus variabilis continued
Bumble Bees of the Eastern United States 85
Bombus variabilis continued
Females (no workers, colors refer to pile or ‘hair’):
• Face black, thorax extensively yellow, but the lower
sides black, tail usually black, hair very short.
• Hind tibia with the outer surface convex and densely
hairy. Hair of the face black with only a minority of pale
hairs above the base of the antenna. Sides of the thorax
predominantly black, thoracic dorsum usually with black
hair, hair on the metasoma usually black. Wings dark
brown, hair on the metasoma very short (shorter on T5
than the length of the last joint of the hind tarsus) and
even. T6 shiny with sparse punctures.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Females
Males
86 Bumble Bees of the Eastern United States
Female Bombus insularis.
Photo Sheila Colla
Indiscriminate bumble bee
• Rare in the Eastern United States.
• Select food plants: Solidago (Goldenrods),
Melilotus (Sweet Clovers), Vaccinium, Trifolium (Clovers)
• Tongue length: short
• Hosts: B. pensylvanicus, B. rufocinctus,
B. ternarius, and B. terricola
• Can be confused with B. fernaldae
Bombus insularis
Bumble Bees of the Eastern United States 87
Lateral image of a female Bombus insularis.
Photo Sheila Colla
Female Bombus insularis face.
Photo Sheila Colla
Bombus insularis continued
88 Bumble Bees of the Eastern United States
Bombus insularis continued
Bumble Bees of the Eastern United States 89
Bombus insularis continued
Females (no workers, colors refer to pile or ‘hair’):
• Face yellow, a black band between the wing
bases, tail with some yellow.
• Hind tibia with the outer surface convex and
densely hairy. Hair of the face with a dense
yellow patch above the base of the antenna,
sometimes some yellow below the base of the
antenna but predominantly black. Black hair
forming a band between the wing bases, sides of
the thorax yellow anteriorly but black ventrally and
posteriorly. T3 always with black hair along the
entire midline but yellow laterally, T4 extensively
yellow laterally. Wings light brown.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Females
Males
90 Bumble Bees of the Eastern United States
Female Bombus ashtoni.
Photo Sheila Colla
Ashton cuckoo bumble bee
• Rare, possibly in decline since the mid-1990s
• Select food plants: Vaccinium, Trifolium (Clovers), Rubus,
Melilotus (Sweet clover), Solidago (Goldenrods)
• Hosts: B. affinis, B. terricola
Bombus ashtoni
Bumble Bees of the Eastern United States 91
Lateral image of a Bombus ashtoni female.
Photo Sheila Colla
Female Bombus ashtoni face.
Photo Sheila Colla
Bombus ashtoni continued
92 Bumble Bees of the Eastern United States
Bombus ashtoni continued
Bumble Bees of the Eastern United States 93
Bombus ashtoni continued
Females (no workers, colors refer to pile or ‘hair’):
• Face black, tail with some white.
• Hind tibia with the outer surface convex and
densely hairy. Hair of the face and the top of
the head black, occasionally with some yellow
hairs at the posterior of the top of the head.
Sides of the thorax predominantly black; hair
of T3-5 laterally variable yellowish-white, but
usually white at least posteriorly in the middle
of T4.
Phenology Chart
APR MAY JUNE JULY AUG SEPT OCT
Females
Males
94 Bumble Bees of the Eastern United States
Male Bombus fernaldae foraging.
Photo Beatriz Moisset
Fernald cuckoo bumble bee
• Uncommon
• Select food plants: Potentilla (Typical Cinquefoils), Rubus,
Trifolium (Clovers), Solidago (Goldenrods)
• Hosts: B. perplexus, B. rufocinctus
• Can be confused with B. insularis
Bombus fernaldae
Bumble Bees of the Eastern United States 95
Lateral image of a female Bombus fernaldae.
Photo Sheila Colla
Female Bombus fernaldae face.
Photo Sheila Colla
Bombus fernaldae continued
96 Bumble Bees of the Eastern United States
Bombus fernaldaecontinued
Bumble Bees of the Eastern United States 97
Bombus fernaldae continued
Females (no workers, colors refer to pile or ‘hair’):
• T1 often yellow. Face black, top of the head and
T4 yellow or cream, T5 black.
• Hind tibia with the outer surface convex and
densely hairy. Hair of the face black. T6 curled
very strongly under the metasoma and pointing
anteriorly, S6 ending distally with a shiny
triangular spine, the lateral keels small. Hair
long and uneven.
98 Bumble Bees of the Eastern United States
1 Pollen baskets present (social species) … 2
- Pollen baskets absent (parasitic species) … 26
2 (1) T1–T4 pile dorsally completely yellow or brown … 3
- T1–T4 pile dorsally not completely yellow or brown … 4
3 (2) Face pile predominantly black; thorax sides with the pile
predominantly yellow … fervidus
- Face pile predominantly yellow; thorax sides with the pile
predominantly black … borealis
4 (2) T2–T3 pile completely yellow, or yellow except T2 with a
small amount of black anteriorly in the middle … 5
- T2–T3 pile with extensive black, orange, or red … 8
5 (4) Cheeks as long as or shorter than broad (L≤B), head round;
wings light brown; T5–T6 pile often with a few white, yellow, or
orange hairs … 6
- Cheeks longer than broad (L>B), head elongate; wings dark
brown; T5–T6 pile completely black … 7
6 (5) Thorax pile with a black band between the wing bases …
terricola
- Thorax pile without a black band between the wing bases …
perplexus
7 (5) Top of the head between the ocelli with the pile entirely
black; T1 pile yellow or black but often with some yellow,
Identification Key
for the female bumble bees
of the Eastern United States
The following dichotomous key
designed by Paul Williams will help
you identify female bumble bee
specimens to species. Starting at the
first set of statements, determine which
characteristics your specimen has
and move to the next appropriate set
(numbered at the end of the statement).
Bumble Bees of the Eastern United States 99
especially in the middle; ocelli located in front of the
supraorbital line by less than one ocellar diameter …
pensylvanicus
- Top of the head between the ocelli with the pile with
some yellow hairs; T1 pile black but often with some
yellow, especially at the sides, fewer yellow hairs in
the middle; ocelli located in front of the supraorbital
line by more than one ocellar diameter … auricomus
8 (4) T3 pile predominantly orange-red, at least away
from the midline … 9
- T3 pile predominatly black, yellow, or pale orange …
10
9 (8) Cheeks as long as broad (L=B); T2 pile
predominatly orange-red, often with some black in the
middle … ternarius
- Cheeks shorter than broad (L<B); T2 pile often
yellow, at least anteriorly in the middle … rufocinctus
10 (8) T3–T4 pile entirely black … 11
- T3–T4 pile with yellow, brown, orange, or red … 24
11 (10) T2 pile completely black … impatiens
- T2 pile with yellow or brown, at least with a few pale
hairs anteriorly in the middle … 12
12 (11) T2 pile brown in the middle and darker than T1
… 13
- T2 pile yellow or brown in the middle but similar to
T1 … 14
13 (12) T2 pile black on the posterior corners …
griseocollis
- T2 pile yellow on the posterior corners … affinis
14 (12) Sides of the thorax with the pile extensively
black … perplexus
- Sides of the thorax with the pile almost completely
yellow … 15
15 (14) T2 pile not completely yellow dorsally as far as
the posterior edge, a patch of entirely black hairs at
least on the posterior dorsal corners … 16
- T2 pile yellow dorsally as far as the posterior edge,
sometimes with a few black hairs but only below
where T2 curves ventrally at the sides … 19
16 (15) Top of the head between ocelli with the pile
black, at most with a few yellow hairs intermixed …
griseocollis
- Top of the head between ocelli with a patch of pile
predominantly yellow … 17
100 Bumble Bees of the Eastern United States
17 (16) Cheeks longer than broad (L>B), head elongate;
T4–T5 pile completely black … 18
- Cheeks shorter than broad (L<B), head round; T4–
T5 pile with or without yellow … rufocinctus
18 (17) T2 pile anteriorly at the sides entirely black; face
pile rarely with yellow … bimaculatus
- T2 pile anteriorly at the sides yellow; face pile
usually with some yellow intermixed … vagans
19 (15) Wings light brown; cheeks nearly as long as
broad or longer (L<B, L>B); T2–T4 pile medium to
long and erect … 20
- Wings dark brown; cheeks very short (L«B), about
half as long as broad; T2–T4 pile very short, even,
and decumbent … fraternus
20 (19) Hind basitarsus with the posterior edge nearly
straight in the distal three quarters; top of the head
between the ocelli with the pile usually predominantly
yellow; body size small to medium (length ≤ 19mm)
… 21
- Hind basitarsus with the posterior edge evenly
arched in the distal three quarters; top of the head
between the ocelli with the pile black with only a
few yellow hairs intermixed; body size usually large
(length ≥20 mm) but includes occasional smaller
individuals … affinis
21 (20) Cheeks shorter than or equal to broad (L≤B),
head round … 22
- Cheeks longer than broad (L>B), head elongate …
23
22 (21) Cheeks shorter than broad (L<B); ocelli located
slightly in front of the supraorbital line … rufocinctus
- Cheeks as long as broad (L=B); ocelli located on the
supraorbital line … sandersoni
23 (21) Thorax pile with many black hairs between the
wing bases; face pile with few or no yellow hairs; T3
pile black … vagans
- Thorax pile with few or no black hairs between
the wing bases; face pile varying from black to
having many yellow hairs; T3 pile black or yellow …
perplexus
24 (10) Cheeks shorter than broad (L<B); ocelli located
slightly in front of the supraorbital line … rufocinctus
- Cheeks as long as broad (L=B); ocelli located on the
supraorbital line … 25
Bumble Bees of the Eastern United States 101
25 (24) T3 pile at least anteriorly partly yellow or brown;
T4 pile often all black, or with some yellow or white
hairs, but never orange … perplexus
- T3 pile predominantly black; T4 pile entirely or at
least posteriorly orange … frigidus
26 (1) T2–T5 pile medium to long and strongly
overlapping, at least partly obscuring the surface;
T1–T6 pile either with yellow, or if entirely black then
the sides of thorax with the pile entirely yellow; wings
light or medium brown; between the wing bases the
pile with or without a black band or spot … 27
- T2–T5 pile very short, scarcely overlapping,
and inconspicuous, the surface very glossy and
unobscured, appearing bare; T1–T6 pile entirely
black; sides of the thorax with the pile predominantly
black; wings dark brown; between the wing bases the
pile always with a black band or spot … variabilis
27 (26) Top of the head between the ocelli with
predominantly yellow pile; sides of the thorax with the
pile predominantly yellow; T4 pile black and/or yellow
or white … 28
- Top of the head between the ocelli with black pile,
at most with a few yellow hairs; sides of the thorax
with the pile predominantly black; T4 pile completely
pale, usually nearly white medially … ashtoni
28 (27) T4 pile black; between wing the bases the pile
without a black band, but sometimes with a black
spot … citrinus
- T4 pile with some yellow or white laterally; between
the wing bases the pile with a black band present or
sometimes with a black spot … 29
29 (28) Face pile black; T1 pile with yellow hairs
laterally; T4 pile predominantly yellow or white; tip of
the abdomen strongly recurved, pointing anteriorly;
S6 apex extending beyond T6 as a curved spine …
fernaldae
- Face pile with a mixture of yellow and black hairs;
T1 pile black; T4 pile predominantly black with yellow
laterally; tip of the abdomen weakly recurved, pointing
ventrally; S6 and T6 equal in length … insularis
102 Bumble Bees of the Eastern United States
Acknowledgements
We gratefully acknowledge help and valuable discussion
from John Ascher, Laurie Davies Adams, Steve
Buchmann, Cory Sheffield, Laurence Packer, Claudia
Ratti, Fawziah Gadallah, James Strange, Chris Plowright,
Liz Day, Elizabeth Sellers, Sam Droege, Laura Burkle,
attendees of the 2009 Bombus Experts Meeting in
Washington, DC, and photograph providers.
Additionally, we would like to thank the following for use
of data for producing range maps:
Caroline Scully, Antioch University New England; John
Ascher, American Museum of Natural History;
Ohio State University Hymenoptera Online Database;
Illinois Natural History Survey; Yale University, Peabody
Museum; University of Connecticut Insect Collections;
University of Vermont’s Zadock Thompson Zoology
Collection; Canadian National Collection of Insects;
Rachael Winfree, Rutgers University; Sam Droege, U.S.
Geological Survey, Patuxent Wildlife Research Center;
Michael Arduser, Missouri Department of Conservation;
Kevin Matteson, Fordham University; Kurt Pickett,
University of Vermont; Helen Young, Middlebury College;
Ross Bell, University of Vermont; Jeff Freeman, Castleton
State College; Don Miller, Lyndon State College; Trish
Hanson, Vermont Department of Forests and Parks;
Vermont Fish and Wildlife Department.
Funding for this project was provided by the Pollinator
Partnership, the U.S. Department of Agriculture Forest
Service, and the National Fish and Wildlife Foundation.
Funding for the high definition camera was provided by
CFI and ORF.
Bumble Bees of the Eastern United States 103
Web and Other Resources
Colour Key to the Bombus of the World by Paul Williams [Online]
http://www.nhm.ac.uk/research-curation/research/projects/bombus/_key_colour_world/worldcolourkey.html
Bumble bee Economics by B. Heinrich, Harvard University Press, 2004.
Bumble bees by D.V. Alford, Davis-Poynter, London, 1974.
Bumble bees: their behaviour and ecology by D. Goulson, Oxford University Press, 2003.
Bumble bee vulnerability and conservation world-wide. Apidologie 40: 367-387. Williams, P.H. & J.L. Osborne.
2009. [Online]
http://www.nhm.ac.uk/research-curation/research/projects/bombus/Williams&Osborne09_review.pdf
Pollinator Partnership www.pollinator.org for Bombus White Paper
Xerces Society of Invertebrate Conservation [Online]
http://www.xerces.org/bumble bees/
Discover Life Bumblebee Key [Online]
http://www.discoverlife.org/mp/20q?guide=v bees
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FS-972
March 2011
