Conservation and 

Management of

North American 

Bumble Bees

By

Dale F. Schweitzer, Nicole A. Capuano, 

Bruce E. Young, and Sheila R. Colla

A product of the USDA Forest Service and NatureServe 

with funding from the National Fish and Wildlife Foundation
Conservation and Management of North American Bumble Bees 

Dale F. Schweitzer1, Nicole A. Capuano1, 

Bruce E. Young1

, and Sheila R. Colla2

1

NatureServe, 4600 North Fiarfax Dr., Floor 7, Arlington, VA 22203

2

Biology Department, York University, Toronto, ON, Canada

Cite this document as: Schweitzer, D.F., N.A. Capuano, B.E. Young, and S.R. Colla. 2012. Conservation and management of North

American bumble bees. NatureServe, Arlington, Virginia, and USDA Forest Service, Washington, D.C.

Report coordination by Pollinator Partnership 

Designer: Marguerite Meyer
Conservation and Management of North American Bumble Bees 

Dale F. Schweitzer1, Nicole A. Capuano1, 

Bruce E. Young1

, and Sheila R. Colla2

1

NatureServe, 4600 North Fiarfax Dr., Floor 7, Arlington, VA 22203

2

Biology Department, York University, Toronto, ON, Canada

Cite this document as: Schweitzer, D.F., N.A. Capuano, B.E. Young, and S.R. Colla. 2012. Conservation and management of North

American bumble bees. NatureServe, Arlington, Virginia, and USDA Forest Service, Washington, D.C.

Report coordination by Pollinator Partnership 

Designer: Marguerite Meyer
4 Conservation and Management of North American Bumble Bees 

Introduction

Bumble bees are a familiar component of 

ourterrestrial fauna.In the past,sighting a bumble bee may have elicited no 

more than a mental note to avoid getting 

stung or at most wonderment at how they 

can be active on high mountains or in 

cold climates. Today we pay them much 

more attention. Precipitous population

declines have affected several species, 

creating cause for conservation concern. 

In addition, the loss of introduced honey

bees(Apis mellifera)in both managed and

feral colonies has increased the need for 

native pollinator species. Bumble bees are 

generalist pollinators, performing a key 

function in their ecosystems. They also 

form a significant portion of the native 

insect community that pollinates crops 

worth $3 billion each year in the United 

States(Losey and Vaughan 2006). For

both of these reasons, land managers are 

increasingly interested in bumble bee 

conservation and management(Goulson

et al. 2010).

This document summarizes recent 

information about bumble bee declines 

and their management in North America. 

By “bumble bee”, we refer to species of 

the genus Bombus (Hymenoptera, Apidae), including the cuckoo bumble bees

in the subgenus Psithyrus. We start with 

a brief overview of bumble bee diversity 

and natural history to provide context 

forthe subsequent discussions. We then

review the conservation status of bumble 

bees and the potential causes for their 

decline. Finally, we discuss considerations 

for managing for bumble bee diversity 

and abundance. Many of the resulting 

recommendations apply to other native 

pollinators besides bumble bees, especially 

ground-nesting bees. Much research

on bumble bee conservation occurs in 

Europe, so we draw on this information 

where appropriate. The bibliographic references provide an entry 

point into the growing literature on 

bumble bees. Because scientific papers on 

bumble bees are being published with increasing frequency (Goulson et al. 2010),

we recognize that this document provides 

a snapshot of the state of our current 

knowledge and thatsubsequentresearch

will fill in some of the knowledge gaps we 

identify here.

Diversity

Of the 250 species of bumble beesrecognized by taxonomists, approximately 46 

occurin the U.S. and Canada (See Appendix for notes on species classification 

used here). All North American species

are native to the continent. Most species 

have fairly broad ranges either east or 

west of the Rockies or across northern 

Canada, although a few such as Bombus franklini in northern California and 

southern Oregon have restricted ranges. 

Six species, including three of the four 

North American species in the subgenus 

Alpinobombus extend their ranges to Asia 

and Europe. As in the rest of the world, 

bumble bee diversity in North America 

is lowest in the southern lowlands and 

highest in cooler northern and mountain 

regions(Figure 1). For example, most

bumble bees in Arizona occur only in the 

mountains. This pattern is opposite of 

most plant and vertebrate groups, which 

generally decrease in diversity with 

latitude.

In North America, the genus Bombus

comprises eight subgenera. These are:

Alpinobombus (4 species)—Bumble

bees of the arctic and high alpine areas.

Bombias (2 species)—A small group

of bumble bees that occur primarily in 

open grasslands.

Bombus (5 species)—“Typical”

bumble bees that occur in a variety of 

temperate and boreal habitats.

Cullumanobombus (5 species)—Mostly bumble bees of high alpine grasslands and semi-desert.

Psithyrus (6 species)—“Cuckoo” bees

that parasitize nests of other bumble 

bees.

Pyrobombus (20 species) —The largest

Figure 1. Documented bumble bee diversity in states or provinces for which 

adequate data are available. Figures for some states may still represent 

underestimates.
4 Conservation and Management of North American Bumble Bees 

Introduction

Bumble bees are a familiar component of 

ourterrestrial fauna.In the past,sighting a bumble bee may have elicited no 

more than a mental note to avoid getting 

stung or at most wonderment at how they 

can be active on high mountains or in 

cold climates. Today we pay them much 

more attention. Precipitous population

declines have affected several species, 

creating cause for conservation concern. 

In addition, the loss of introduced honey

bees(Apis mellifera)in both managed and

feral colonies has increased the need for 

native pollinator species. Bumble bees are 

generalist pollinators, performing a key 

function in their ecosystems. They also 

form a significant portion of the native 

insect community that pollinates crops 

worth $3 billion each year in the United 

States(Losey and Vaughan 2006). For

both of these reasons, land managers are 

increasingly interested in bumble bee 

conservation and management(Goulson

et al. 2010).

This document summarizes recent 

information about bumble bee declines 

and their management in North America. 

By “bumble bee”, we refer to species of 

the genus Bombus (Hymenoptera, Apidae), including the cuckoo bumble bees

in the subgenus Psithyrus. We start with 

a brief overview of bumble bee diversity 

and natural history to provide context 

forthe subsequent discussions. We then

review the conservation status of bumble 

bees and the potential causes for their 

decline. Finally, we discuss considerations 

for managing for bumble bee diversity 

and abundance. Many of the resulting 

recommendations apply to other native 

pollinators besides bumble bees, especially 

ground-nesting bees. Much research

on bumble bee conservation occurs in 

Europe, so we draw on this information 

where appropriate. The bibliographic references provide an entry 

point into the growing literature on 

bumble bees. Because scientific papers on 

bumble bees are being published with increasing frequency (Goulson et al. 2010),

we recognize that this document provides 

a snapshot of the state of our current 

knowledge and thatsubsequentresearch

will fill in some of the knowledge gaps we 

identify here.

Diversity

Of the 250 species of bumble beesrecognized by taxonomists, approximately 46 

occurin the U.S. and Canada (See Appendix for notes on species classification 

used here). All North American species

are native to the continent. Most species 

have fairly broad ranges either east or 

west of the Rockies or across northern 

Canada, although a few such as Bombus franklini in northern California and 

southern Oregon have restricted ranges. 

Six species, including three of the four 

North American species in the subgenus 

Alpinobombus extend their ranges to Asia 

and Europe. As in the rest of the world, 

bumble bee diversity in North America 

is lowest in the southern lowlands and 

highest in cooler northern and mountain 

regions(Figure 1). For example, most

bumble bees in Arizona occur only in the 

mountains. This pattern is opposite of 

most plant and vertebrate groups, which 

generally decrease in diversity with 

latitude.

In North America, the genus Bombus

comprises eight subgenera. These are:

Alpinobombus (4 species)—Bumble

bees of the arctic and high alpine areas.

Bombias (2 species)—A small group

of bumble bees that occur primarily in 

open grasslands.

Bombus (5 species)—“Typical”

bumble bees that occur in a variety of 

temperate and boreal habitats.

Cullumanobombus (5 species)—Mostly bumble bees of high alpine grasslands and semi-desert.

Psithyrus (6 species)—“Cuckoo” bees

that parasitize nests of other bumble 

bees.

Pyrobombus (20 species) —The largest

Figure 1. Documented bumble bee diversity in states or provinces for which 

adequate data are available. Figures for some states may still represent 

underestimates.
6 Conservation and Management of North American Bumble Bees 

visiting hundreds of native and introduced plant genera (Robertson 1929,

Mitchell 1962, Colla and Dumesh 2010).

Some species are more generalized in 

their foraging preferences than others, 

but none appear to be highly specialized. 

In one study in Iowa prairie remnants,

bumble beesforaged at 43 of 150 species

of flowers available (Hines and Hendrix

2005). However, the extent ofspecialism

at the colony or individual level is largely 

unknown.

Activity and cold tolerance.—Bumble

bees are well known to fly when conditions are too cold for most other insects 

(e.g. cloudy or cool days, or early in the

morning before other diurnal insects are 

active). They have a low surface area to

volume ratio compared to other insects, 

are well insulated, and can generate body 

heat using their thoracic muscles. Bumble 

bees have been reported flying atslightly

sub-freezing temperatures(Heinrich

1979). This ability to fly in cold weather

is undoubtedly a factor in the success 

of bumble bees in cool to frigid climates 

throughout much of the world. 

Bumble bees’ seasonal activity differs 

among species.In the Mid-Atlantic states,

activity starts about the end of March for 

the earliest species and becomes minimal 

in October(Droege 2008). Some early

species such as B. impatiens are active 

into the fall, while others end their cycles 

in June or July (e.g., B. bimaculatus). 

Others, including B. pensylvanicus, emerge 

from their overwintering sites later in 

spring. The parasitic cuckoo species also 

tend to have shorter cycles.In northern

New England, activity begins a month or 

more later and ends a few weeks earlier. A 

good rule of thumb in much of the eastern 

U.S. isthat queens of the early-emerging

species become numerous soon after red 

maple (Acer rubrum) blossoms drop and

just before blueberry (Vaccinium spp.)

and other early Ericaceae flower. Early

emerging species also tend to be associated with woodland habitats, whereas the 

later emerging species tend to be associated with more 

open habitat(Colla

and Dumesh 2010). The

disappearance of bumble 

bees in the fall appears to 

be timed with the passing 

of native fall flowers and

often precedes the first frost 

and leaf fall(D. Schweitzer,

pers. obs.).

Nest usurpation.— Species of subgenus Psithyrus

have no worker caste of their own. 

Females can reproduce only by taking 

over a nest of another species. Workers 

in usurped nests tend the offspring of the 

replacement queen. Entomologists have

not fully documented the host breadth of 

North American Psithyrus. Bombus insularis preys on several subgenera, whereas 

B. citrinus is apparently a specialist on 

subgenus Pyrobombus. Bombus ashtoni

and B. suckleyi seem to be specialists on 

the subgenus Bombus (Williams 2008b,

Laverty and Harder 1988), and B. variabilis appears to be a specialist on B. pensylvanicus. Queens of subgenera Alpinobombus and Bombus sometimes usurp nests 

of their own or closely related species 

(Richards 1973, Goulson 2010).

Aggression.—Bumble bees occasionally sting when their nest is disturbed, 

but rarely do so otherwise. Queens and 

workers can sting, but, as in all bees and 

wasps, males cannot. To humans, the 

stings are briefly painful but not dangerous, except to a few people who develop 

serious allergic reactions. Bumble bee 

hives contain far fewer individuals than 

those of honey bees, and workers of most 

species are far less aggressive than wasps 

and hornets. Bumble bee stingers are not 

barbed as in honey bees and therefore do 

notremain in the victim. However, this

also means a bumble bee can sting more 

than once when provoked. Some species, 

such as B. impatiens, are remarkably nonaggressive when nesting around buildings. 

This species is also safely managed for 

crop pollination, including in greenhouses. 

Workers of other species, such as B. 

pensylvanicus, and B. fervidus can be very 

aggressive around their nests(Thorp et al.

1983, Kearns and Thomson 2001), likely

a behavioral adaptation to their aboveground nesting habits. 

Pollination.—Bumble bees are important generalist pollinators of native plants 

and agricultural crops. The list of flowers

visited by bumble beesis vast(Goulson

2010, Kearns and Thomson 2001, Thorp

et al. 1983). Theoreticalstudies have underscored the importance of generalists in 

maintaining pollinator networks and communities of flowering plants(Memmott et

al. 2004). One empiricalstudy in Europe

confirmed this prediction, demonstrating 

that the abundance of insect-pollinated

plants declined in areas where bumble 

bees and other native bees had become 

extirpated (Biesmeijer et al. 2006).

Bumble bees exhibit a behavior known 

as “buzz pollination,” in which the bee 

vibrates her wing muscles while holding 

the flower with herjaws, causing the release of large amounts of pollen. Growers

of crops such as tomatoes, peppers, and 

cranberries prize this behavior because 

it leads to better fruit set than pollination 

by honey bees. A commercial bumble 

bee industry has emerged to capitalize on 

buzz pollination for greenhouse tomato 

farmers(Velthius and van Doorn 2006), a

development that may have had the unin

Figure 2. Proportion of North American 

bumble bee species at risk.
6 Conservation and Management of North American Bumble Bees 

visiting hundreds of native and introduced plant genera (Robertson 1929,

Mitchell 1962, Colla and Dumesh 2010).

Some species are more generalized in 

their foraging preferences than others, 

but none appear to be highly specialized. 

In one study in Iowa prairie remnants,

bumble beesforaged at 43 of 150 species

of flowers available (Hines and Hendrix

2005). However, the extent ofspecialism

at the colony or individual level is largely 

unknown.

Activity and cold tolerance.—Bumble

bees are well known to fly when conditions are too cold for most other insects 

(e.g. cloudy or cool days, or early in the

morning before other diurnal insects are 

active). They have a low surface area to

volume ratio compared to other insects, 

are well insulated, and can generate body 

heat using their thoracic muscles. Bumble 

bees have been reported flying atslightly

sub-freezing temperatures(Heinrich

1979). This ability to fly in cold weather

is undoubtedly a factor in the success 

of bumble bees in cool to frigid climates 

throughout much of the world. 

Bumble bees’ seasonal activity differs 

among species.In the Mid-Atlantic states,

activity starts about the end of March for 

the earliest species and becomes minimal 

in October(Droege 2008). Some early

species such as B. impatiens are active 

into the fall, while others end their cycles 

in June or July (e.g., B. bimaculatus). 

Others, including B. pensylvanicus, emerge 

from their overwintering sites later in 

spring. The parasitic cuckoo species also 

tend to have shorter cycles.In northern

New England, activity begins a month or 

more later and ends a few weeks earlier. A 

good rule of thumb in much of the eastern 

U.S. isthat queens of the early-emerging

species become numerous soon after red 

maple (Acer rubrum) blossoms drop and

just before blueberry (Vaccinium spp.)

and other early Ericaceae flower. Early

emerging species also tend to be associated with woodland habitats, whereas the 

later emerging species tend to be associated with more 

open habitat(Colla

and Dumesh 2010). The

disappearance of bumble 

bees in the fall appears to 

be timed with the passing 

of native fall flowers and

often precedes the first frost 

and leaf fall(D. Schweitzer,

pers. obs.).

Nest usurpation.— Species of subgenus Psithyrus

have no worker caste of their own. 

Females can reproduce only by taking 

over a nest of another species. Workers 

in usurped nests tend the offspring of the 

replacement queen. Entomologists have

not fully documented the host breadth of 

North American Psithyrus. Bombus insularis preys on several subgenera, whereas 

B. citrinus is apparently a specialist on 

subgenus Pyrobombus. Bombus ashtoni

and B. suckleyi seem to be specialists on 

the subgenus Bombus (Williams 2008b,

Laverty and Harder 1988), and B. variabilis appears to be a specialist on B. pensylvanicus. Queens of subgenera Alpinobombus and Bombus sometimes usurp nests 

of their own or closely related species 

(Richards 1973, Goulson 2010).

Aggression.—Bumble bees occasionally sting when their nest is disturbed, 

but rarely do so otherwise. Queens and 

workers can sting, but, as in all bees and 

wasps, males cannot. To humans, the 

stings are briefly painful but not dangerous, except to a few people who develop 

serious allergic reactions. Bumble bee 

hives contain far fewer individuals than 

those of honey bees, and workers of most 

species are far less aggressive than wasps 

and hornets. Bumble bee stingers are not 

barbed as in honey bees and therefore do 

notremain in the victim. However, this

also means a bumble bee can sting more 

than once when provoked. Some species, 

such as B. impatiens, are remarkably nonaggressive when nesting around buildings. 

This species is also safely managed for 

crop pollination, including in greenhouses. 

Workers of other species, such as B. 

pensylvanicus, and B. fervidus can be very 

aggressive around their nests(Thorp et al.

1983, Kearns and Thomson 2001), likely

a behavioral adaptation to their aboveground nesting habits. 

Pollination.—Bumble bees are important generalist pollinators of native plants 

and agricultural crops. The list of flowers

visited by bumble beesis vast(Goulson

2010, Kearns and Thomson 2001, Thorp

et al. 1983). Theoreticalstudies have underscored the importance of generalists in 

maintaining pollinator networks and communities of flowering plants(Memmott et

al. 2004). One empiricalstudy in Europe

confirmed this prediction, demonstrating 

that the abundance of insect-pollinated

plants declined in areas where bumble 

bees and other native bees had become 

extirpated (Biesmeijer et al. 2006).

Bumble bees exhibit a behavior known 

as “buzz pollination,” in which the bee 

vibrates her wing muscles while holding 

the flower with herjaws, causing the release of large amounts of pollen. Growers

of crops such as tomatoes, peppers, and 

cranberries prize this behavior because 

it leads to better fruit set than pollination 

by honey bees. A commercial bumble 

bee industry has emerged to capitalize on 

buzz pollination for greenhouse tomato 

farmers(Velthius and van Doorn 2006), a

development that may have had the unin

Figure 2. Proportion of North American 

bumble bee species at risk.
8 Conservation and Management of North American Bumble Bees 

on more natural habitats. Some agricultural habitats, such as hay meadows and 

pastures, are suitable to bumble bees 

(Carvell 2002, Goulson 2010, McFrederick and LeBuhn 2006, Rao and Stephen

2010). Some species can even prosperin

urban gardens and parks(McFrederick

and LeBuhn 2006, Matteson et al. 2008,

Matteson and Langellotto 2009). The

spread of Eurasian clovers(Trifolium)

and vetches(Vicia, Coronilla) has benefited some butterflies(Schweitzer 2006)

and presumably bumble bees as well. 

Nevertheless, intensive agriculture has 

caused local and regional declines in the 

Midwest as well as Europe (Grixti et al.

2009, Williams et al. 2009). The mismatch

between the time scale of habitat loss 

(before the mid 20th century) and rapidly

declining North American species(since

the mid 1990s)suggeststhat habitat lossis

unlikely to explain these declines(Grixti

et al. 2009).

Climate change.—Although climate

change has been suggested as a cause of 

declines and may be affecting bumble 

bees in some places, there is as of yet little 

direct evidence that climate change is 

responsible for global declines of widespread species.In North America, most

species occur(at least formerly)in a wide

array of climates, ranging through more 

than ten degrees of latitude and some 

from coast to coast. Moreover, most of 

the North American species that have 

declined precipitously had large ranges. 

Even B. affinis ranged from Maine to 

Georgia and the Dakotas(Figure 3).

Despite this large range, members of the 

subgenus Bombus do seem to be somewhat climatically restricted as they occur 

mostly at high elevations in southern parts 

of their ranges. Range breadth, combined 

with high mobility and dispersal ability, 

and the observed rapidity of declines seem 

to argue against climate change as being 

a major factor in recent dramatic declines. 

However, more research is needed to

further investigate this.

Species that may prove to be vulnerable 

to climate change are those that 

occupy narrow ranges nearthe Pacific

coast, such as B. crotchii in oak woodland, 

chaparral, and deserts and B. sitkensis and 

B. caliginosus in cooler coastal climates. 

Elsewhere, isolated high alpine populations of several species may disappear due 

to climate change.

Phenology of queen emergence.—

Some authors suggest that species in 

which queens become active laterin

the season are at a disadvantage due to 

competition for nest sites and vulnerability 

to losses of food plants that are important in mid to late colony development 

(Williams et al. 2009).In North America,

nest competition is documented in urban 

areas of San Francisco where the early 

B. vosnenskii apparently excludes the 

later B. caliginosus and B. sitkensis from 

the limited supply of subterranean nest 

sites(McFrederick and LeBuhn 2006).

However, none of these species appearto

be declining globally, and there is no evidence that phenology is linked to declines 

of bumble bees in North America where 

both early- and late-emerging species are

among the five non-parasitic speciesthat

are in severe decline. 

Tongue length and foraging ecology.—Bumble bees with long tongues are

generally more specialized foragers. Although some authors have suggested that 

specialists(and therefore longer-tongued

species)should be more likely to decline,

no such pattern has emerged in North 

America (Grixti et al. 2009, Williams et al.

2009, Winfree 2010). One complication

with relating tongue length with foraging is that tongue length is individually 

variable with body size, whereas foraging 

preferences are largely learned (Kearns

and Thomson 2001). Direct measures of

foraging specialization, however, indicate 

a weak relationship with declines in Europe (Kleijn and Raemakers 2008).

Pesticides.—Direct exposure to pesticides

can kill queen or worker bumble bees,

and cause minor to lethal effects to larvae 

that feed on pesticide-contaminated food.

Some pesticides, such as spinosad, cause 

no direct mortality but instead reduce 

foraging efficiency (Goulson 2010). The

toxicity of specific pesticides is better 

known for honey bees than bumble bees, 

but the available data suggest that toxicity 

to bumble bees is generally similar to that 

of honey bees(Alston and Tepedino 2000).

An application of pesticides to control 

spruce budworm in New Brunswick illustrates the potential effects of pesticides 

on bumble bees and other pollinators.In

this case, the pesticide application caused 

blueberry crop losses due to reduced availability of pollinators.In addition,reduced

pollination of nearby native species caused 

a local wild berry shortage and consequently increased the number of birds

foraging on cultivated blueberries(Kevan

1974). Bumble bee colonies can absorb the

loss of a few workers to pesticides in summer, but worker loss can more seriously 

impact colony survival in spring before 

colonies have built up significant numbers 

of workers(Goulson 2010). Additionally,

sub-lethal compounds may accumulate in

the colony and affect the overall reproductive fitness of the colony. Species which 

may be more vulnerable to pesticide use 

include the above ground nesting species(e.g.,subgenus Thoracobombus) and

species with long colony cycles that can 

accumulate toxins over the spring, summer and fall. Pesticideslikely contribute to

bumble bee declines in areas of intensive 

agriculture, but are unlikely to be responsible forrapid, widespread declines(Colla

and Packer 2008, DeVore 2009).

Pathogen spillover.—Currently, the

most compelling hypothesis to explain 

rapid declines is the spillover of pathogens 

from managed to wild bumble bees(Colla

et al. 2006, Otterstatter and Thomson 

2008, Williams et al. 2009, Goulson 2010,

Meeus et al. 2011). Field documentation of pathogen spillover and related 

modeling show waves of parasites and 

pathogens spreading out from infested 

commercial hives at multiple locations. 

Moreover, the timing of decline onset in 
8 Conservation and Management of North American Bumble Bees 

on more natural habitats. Some agricultural habitats, such as hay meadows and 

pastures, are suitable to bumble bees 

(Carvell 2002, Goulson 2010, McFrederick and LeBuhn 2006, Rao and Stephen

2010). Some species can even prosperin

urban gardens and parks(McFrederick

and LeBuhn 2006, Matteson et al. 2008,

Matteson and Langellotto 2009). The

spread of Eurasian clovers(Trifolium)

and vetches(Vicia, Coronilla) has benefited some butterflies(Schweitzer 2006)

and presumably bumble bees as well. 

Nevertheless, intensive agriculture has 

caused local and regional declines in the 

Midwest as well as Europe (Grixti et al.

2009, Williams et al. 2009). The mismatch

between the time scale of habitat loss 

(before the mid 20th century) and rapidly

declining North American species(since

the mid 1990s)suggeststhat habitat lossis

unlikely to explain these declines(Grixti

et al. 2009).

Climate change.—Although climate

change has been suggested as a cause of 

declines and may be affecting bumble 

bees in some places, there is as of yet little 

direct evidence that climate change is 

responsible for global declines of widespread species.In North America, most

species occur(at least formerly)in a wide

array of climates, ranging through more 

than ten degrees of latitude and some 

from coast to coast. Moreover, most of 

the North American species that have 

declined precipitously had large ranges. 

Even B. affinis ranged from Maine to 

Georgia and the Dakotas(Figure 3).

Despite this large range, members of the 

subgenus Bombus do seem to be somewhat climatically restricted as they occur 

mostly at high elevations in southern parts 

of their ranges. Range breadth, combined 

with high mobility and dispersal ability, 

and the observed rapidity of declines seem 

to argue against climate change as being 

a major factor in recent dramatic declines. 

However, more research is needed to

further investigate this.

Species that may prove to be vulnerable 

to climate change are those that 

occupy narrow ranges nearthe Pacific

coast, such as B. crotchii in oak woodland, 

chaparral, and deserts and B. sitkensis and 

B. caliginosus in cooler coastal climates. 

Elsewhere, isolated high alpine populations of several species may disappear due 

to climate change.

Phenology of queen emergence.—

Some authors suggest that species in 

which queens become active laterin

the season are at a disadvantage due to 

competition for nest sites and vulnerability 

to losses of food plants that are important in mid to late colony development 

(Williams et al. 2009).In North America,

nest competition is documented in urban 

areas of San Francisco where the early 

B. vosnenskii apparently excludes the 

later B. caliginosus and B. sitkensis from 

the limited supply of subterranean nest 

sites(McFrederick and LeBuhn 2006).

However, none of these species appearto

be declining globally, and there is no evidence that phenology is linked to declines 

of bumble bees in North America where 

both early- and late-emerging species are

among the five non-parasitic speciesthat

are in severe decline. 

Tongue length and foraging ecology.—Bumble bees with long tongues are

generally more specialized foragers. Although some authors have suggested that 

specialists(and therefore longer-tongued

species)should be more likely to decline,

no such pattern has emerged in North 

America (Grixti et al. 2009, Williams et al.

2009, Winfree 2010). One complication

with relating tongue length with foraging is that tongue length is individually 

variable with body size, whereas foraging 

preferences are largely learned (Kearns

and Thomson 2001). Direct measures of

foraging specialization, however, indicate 

a weak relationship with declines in Europe (Kleijn and Raemakers 2008).

Pesticides.—Direct exposure to pesticides

can kill queen or worker bumble bees,

and cause minor to lethal effects to larvae 

that feed on pesticide-contaminated food.

Some pesticides, such as spinosad, cause 

no direct mortality but instead reduce 

foraging efficiency (Goulson 2010). The

toxicity of specific pesticides is better 

known for honey bees than bumble bees, 

but the available data suggest that toxicity 

to bumble bees is generally similar to that 

of honey bees(Alston and Tepedino 2000).

An application of pesticides to control 

spruce budworm in New Brunswick illustrates the potential effects of pesticides 

on bumble bees and other pollinators.In

this case, the pesticide application caused 

blueberry crop losses due to reduced availability of pollinators.In addition,reduced

pollination of nearby native species caused 

a local wild berry shortage and consequently increased the number of birds

foraging on cultivated blueberries(Kevan

1974). Bumble bee colonies can absorb the

loss of a few workers to pesticides in summer, but worker loss can more seriously 

impact colony survival in spring before 

colonies have built up significant numbers 

of workers(Goulson 2010). Additionally,

sub-lethal compounds may accumulate in

the colony and affect the overall reproductive fitness of the colony. Species which 

may be more vulnerable to pesticide use 

include the above ground nesting species(e.g.,subgenus Thoracobombus) and

species with long colony cycles that can 

accumulate toxins over the spring, summer and fall. Pesticideslikely contribute to

bumble bee declines in areas of intensive 

agriculture, but are unlikely to be responsible forrapid, widespread declines(Colla

and Packer 2008, DeVore 2009).

Pathogen spillover.—Currently, the

most compelling hypothesis to explain 

rapid declines is the spillover of pathogens 

from managed to wild bumble bees(Colla

et al. 2006, Otterstatter and Thomson 

2008, Williams et al. 2009, Goulson 2010,

Meeus et al. 2011). Field documentation of pathogen spillover and related 

modeling show waves of parasites and 

pathogens spreading out from infested 

commercial hives at multiple locations. 

Moreover, the timing of decline onset in 
10 Conservation and Management of North American Bumble Bees 

habitats managed as natural lands, native 

flowering plants will be important.In

other contexts, non-native crops, pasture plants, weeds, and garden flowers

may all be good food sources.In some

agricultural areas successive crops will 

provide a reliable supply of pollen and 

nectar throughout the season, but in other 

contexts supplemental sources such as native vegetation may increase bumble bee 

abundance and diversity (DeVore 2009).

Overall flower abundance and flowering

plant species richness appear to be important for bumble bee richness(Carvell

2002). Variation in tongue length among

bumble bee species causes variation in 

preferencesfor flowertypes. Maintaining

abundant, phenologically and morphologically diverse plants is therefore a prudent 

management approach. 

Because of the diversity of habitats and 

bumble bee faunas across North America, 

we cannot make specific generalizations 

about particular plants that promote bumble bee diversity and abundance. Several 

studies list plants visited by bumble bees, 

including declining species, in particular 

regions(USFWS 1999, 2008; Evans et

al. 2008; Hopwood 2008; Tuell et al. 2008;

DeVore 2009, Colla and Dumesh 2010).

Examples of plantsfavored by longtongued species are legumes, such as red 

clover, and Delphinium (Pyke 1982).

The effect of mowing during the growing 

season on bumble bee colony health is 

debatable but in practice is probably detrimental to the pollinator community. Mowing virtually eliminates nectar for a period 

of days or longer and therefore can stress 

colonies. However,summer mowing can

stimulate re-flowering that benefitsthe

beeslaterin the season (Noordijk et al.

2009).In areas where mowing is essential

for economic activity, staggering cutting 

times will help ensure a continuous food 

supply (Noordijk et al. 2009).

Nesting habitat.—In some places, nest

sites can be a limiting resource and may 

affect both the abundance and diversity of 

bumble bees(Kearns and Thomson 2001,

McFrederick and LeBuhn

2006). Managersshould remember

that some bumble bees nest underground whereas others nest above ground. 

Reducing tillage or leaving unplowed 

strips of vegetation will usually increase 

the availability of nesting habitat for 

ground-nesting species(Hopwood 2008,

DeVore 2009). Fence rows,roadsides,

powerline cuts, and fallow fields can also 

serve this purpose.In areas with limited

nesting habitat, managers can increase 

bumble bee abundance by providing 

artificial nests.

Above-ground nesters often use abandoned rodent and ground-nesting bird

nests(Kearns and Thomson 2001,

McFrederick and LeBuhn 2006). Thus

any management practice that promotes 

rodent and ground-nesting bird populations, including reducing numbers of feral 

and domestic cats(Felis catus), could

have side benefits for bumble bees. When 

rodent and bird nests are not available, 

logs, stumps, snags, and clumps of grass 

are often suitable (DeVore 2009). Recognizing that some bumble bees nest above 

ground, managers should be careful 

not to set mower blades low enough to 

destroy these nests. Also, they should be 

aware that fires are likely to destroy above 

ground nests.

Landscape context.—Landscape

context may be important for bumble bee 

management, but an impediment to assessing factors such as habitat fragmentation is defining unsuitable habitat. Bumble 

beesrequire three different habitat types

(i.e. foraging, nesting and overwintering)

in close proximity to each other, adding 

further complexity. Bumble bee species 

vary in whether anthropogenic habitats 

are favorable or unfavorable habitats 

(McFrederick and LeBuhn 2006, Goulson 2010). Nevertheless,studiestypically

find more bumble bees in landscapes 

with patches of uncultivated lands than in 

intensive agricultural areas.In most cases,

the availability of floralresources within

500-800 m (0.3-0.5 mi) ofsurvey points

explained much of the variance in bumble 

bee communities(Hines and Hendrix

2005, McFrederick and LeBuhn 2006,

Hatfield and LeBuhn 2007, Holzschuh et

al. 2007, Öckinger and Smith 2007, Hopwood 2008, Goulson 2010, Winfree 2010,

Carvell et al. 2011). A study near Boston,

Massachusetts, found that bumble bees 

are reluctant to cross roads and railroads 

when foraging, implying that transportation corridors may be detrimental 

(Bhattacharya et al. 2003). The emerging consensus is that bumble bees need 

nesting and foraging habitat in relatively 

close proximity without dispersal barriers 

between them.

Pesticides.—Pesticide use reduces pollination by bumble bees and may even 

eliminate them from agricultural areas 

(Goulson 2010). However, because

most research on toxicity and effects of 

pesticides are performed on honey bees 

(Girolami et al. 2009), the extent to which

the results of these studies are applicable 

to bumble bees is unknown. We know, 

however, that insecticides are generally 

of greater concern than herbicides. Most 

herbicides probably do not harm bees 

directly, but their use can greatly reduce nectar supplies, which in turn limit 

bumble bee colony success. Absorbing 

insecticide toxins through the exoskeleton, drinking toxin-tainted nectar, or

gathering contaminated pollen or microencapsulated insecticides can kill bumble 

bees directly (Vaughan and Black 2007).

Bumble bees can also carry toxins on 

pollen and nectar to the hive where they 

can kill adults and kill or cause developmental delays in larvae. Sublethal doses of 

toxins can cause colony failure by causing impaired navigation, flight difficulty,

decreased foraging efficiency or inability 

to tend young in the hive (Vaughan and

Black 2007, Mommaerts et al 2010).

The best means of preventing negative impacts of pesticides on bumble 

bees is to avoid applying insecticides to 

patches of flowersthat attract bumble

bees(Vaughan and Black 2007, Black
10 Conservation and Management of North American Bumble Bees 

habitats managed as natural lands, native 

flowering plants will be important.In

other contexts, non-native crops, pasture plants, weeds, and garden flowers

may all be good food sources.In some

agricultural areas successive crops will 

provide a reliable supply of pollen and 

nectar throughout the season, but in other 

contexts supplemental sources such as native vegetation may increase bumble bee 

abundance and diversity (DeVore 2009).

Overall flower abundance and flowering

plant species richness appear to be important for bumble bee richness(Carvell

2002). Variation in tongue length among

bumble bee species causes variation in 

preferencesfor flowertypes. Maintaining

abundant, phenologically and morphologically diverse plants is therefore a prudent 

management approach. 

Because of the diversity of habitats and 

bumble bee faunas across North America, 

we cannot make specific generalizations 

about particular plants that promote bumble bee diversity and abundance. Several 

studies list plants visited by bumble bees, 

including declining species, in particular 

regions(USFWS 1999, 2008; Evans et

al. 2008; Hopwood 2008; Tuell et al. 2008;

DeVore 2009, Colla and Dumesh 2010).

Examples of plantsfavored by longtongued species are legumes, such as red 

clover, and Delphinium (Pyke 1982).

The effect of mowing during the growing 

season on bumble bee colony health is 

debatable but in practice is probably detrimental to the pollinator community. Mowing virtually eliminates nectar for a period 

of days or longer and therefore can stress 

colonies. However,summer mowing can

stimulate re-flowering that benefitsthe

beeslaterin the season (Noordijk et al.

2009).In areas where mowing is essential

for economic activity, staggering cutting 

times will help ensure a continuous food 

supply (Noordijk et al. 2009).

Nesting habitat.—In some places, nest

sites can be a limiting resource and may 

affect both the abundance and diversity of 

bumble bees(Kearns and Thomson 2001,

McFrederick and LeBuhn

2006). Managersshould remember

that some bumble bees nest underground whereas others nest above ground. 

Reducing tillage or leaving unplowed 

strips of vegetation will usually increase 

the availability of nesting habitat for 

ground-nesting species(Hopwood 2008,

DeVore 2009). Fence rows,roadsides,

powerline cuts, and fallow fields can also 

serve this purpose.In areas with limited

nesting habitat, managers can increase 

bumble bee abundance by providing 

artificial nests.

Above-ground nesters often use abandoned rodent and ground-nesting bird

nests(Kearns and Thomson 2001,

McFrederick and LeBuhn 2006). Thus

any management practice that promotes 

rodent and ground-nesting bird populations, including reducing numbers of feral 

and domestic cats(Felis catus), could

have side benefits for bumble bees. When 

rodent and bird nests are not available, 

logs, stumps, snags, and clumps of grass 

are often suitable (DeVore 2009). Recognizing that some bumble bees nest above 

ground, managers should be careful 

not to set mower blades low enough to 

destroy these nests. Also, they should be 

aware that fires are likely to destroy above 

ground nests.

Landscape context.—Landscape

context may be important for bumble bee 

management, but an impediment to assessing factors such as habitat fragmentation is defining unsuitable habitat. Bumble 

beesrequire three different habitat types

(i.e. foraging, nesting and overwintering)

in close proximity to each other, adding 

further complexity. Bumble bee species 

vary in whether anthropogenic habitats 

are favorable or unfavorable habitats 

(McFrederick and LeBuhn 2006, Goulson 2010). Nevertheless,studiestypically

find more bumble bees in landscapes 

with patches of uncultivated lands than in 

intensive agricultural areas.In most cases,

the availability of floralresources within

500-800 m (0.3-0.5 mi) ofsurvey points

explained much of the variance in bumble 

bee communities(Hines and Hendrix

2005, McFrederick and LeBuhn 2006,

Hatfield and LeBuhn 2007, Holzschuh et

al. 2007, Öckinger and Smith 2007, Hopwood 2008, Goulson 2010, Winfree 2010,

Carvell et al. 2011). A study near Boston,

Massachusetts, found that bumble bees 

are reluctant to cross roads and railroads 

when foraging, implying that transportation corridors may be detrimental 

(Bhattacharya et al. 2003). The emerging consensus is that bumble bees need 

nesting and foraging habitat in relatively 

close proximity without dispersal barriers 

between them.

Pesticides.—Pesticide use reduces pollination by bumble bees and may even 

eliminate them from agricultural areas 

(Goulson 2010). However, because

most research on toxicity and effects of 

pesticides are performed on honey bees 

(Girolami et al. 2009), the extent to which

the results of these studies are applicable 

to bumble bees is unknown. We know, 

however, that insecticides are generally 

of greater concern than herbicides. Most 

herbicides probably do not harm bees 

directly, but their use can greatly reduce nectar supplies, which in turn limit 

bumble bee colony success. Absorbing 

insecticide toxins through the exoskeleton, drinking toxin-tainted nectar, or

gathering contaminated pollen or microencapsulated insecticides can kill bumble 

bees directly (Vaughan and Black 2007).

Bumble bees can also carry toxins on 

pollen and nectar to the hive where they 

can kill adults and kill or cause developmental delays in larvae. Sublethal doses of 

toxins can cause colony failure by causing impaired navigation, flight difficulty,

decreased foraging efficiency or inability 

to tend young in the hive (Vaughan and

Black 2007, Mommaerts et al 2010).

The best means of preventing negative impacts of pesticides on bumble 

bees is to avoid applying insecticides to 

patches of flowersthat attract bumble

bees(Vaughan and Black 2007, Black
12 Conservation and Management of North American Bumble Bees 

Acknowledgments

We thank John S. Ascher, American Museum of Natural History, for comments on this manuscript, and Samuel W. Droege, Patuxent Wildlife Research Center, U.S. Geological Survey, and Leif Richardson, Vermont Fish and Wildlife Department, for providing

information on several species. 

Internet Resources

The Bee Genera of Eastern Canada.—A usefulreference for distinguishing the bee genera of eastern Canada.(http://www.biology.ualberta.ca/

bsc/ejournal/pgs_03/pgs_03.html)

Bombus Bumblebees of the World.—Williams(2008a) checklist of the species of the world.(http://www.nhm.ac.uk/research-curation/

research/projects/bombus/index.html)

Bug Guide.—A resource for bumble bee identification, images, and information.(http://bugguide.net/node/view/3077)

Bumble Bee Conservation.—Linksto many useful conservation documents, created by the Xerces Society.(http://www.xerces.org/

bumblebees/)

Bumblebee Pages.—General bumble bee information for beginners.(http://www.bumblebee.org/)

Guide to Bumble bees.—An online key most useful forspecies of the eastern U.S.(http://www.discoverlife.org/mp/20q?guide=Bumblebees)

Plants for Pollinators.—Recommendations on plantsthat will enhance pollinator populations.(http://plant-materials.nrcs.usda.gov/technical/

pollinators.html)

Pollinator Partnership.—Information on protecting pollinatorsthrough conservation, education, and research.(http://www.pollinator.org)

References Cited

Alston, D. G., and V.J. Tepedino. 2000. Direct and indirect effects of insecticides on native bees. Pages 4-1 – 4-4 in Grasshopperintegrated

pest management user handbook (Technical Bulletin No. 1809), edited by G.L. Cuningham and M.W. Sampson. United States Department

of Agriculture Animal and Plant Health Inspection Services, Washington, D.C.

Bertsch, A., M. Hrabé de Angelis, and G.K.H. Przemeck. 2010. A phylogenetic framework forthe North American bumble bee species of

the subgenus Bombus sensu stricto (Bombus affinis, B. franklini, B. moderatus, B. occidentalis & B. terricola) based on mitochondrial DNA

markers. Beiträge zur Entomologie 60:229-242.

Biesmeijer, J.C., S.P.M. Roberts, M. Reemer, R. Ohlemüller, M. Edwards, T. Peeters, A.P. Schaffers, S.G. Potts, R. Kleukers, C.D. Thomas,

J. Settele, and W.E. Kunin. 2006. Parallel declinesin pollinators and insect-pollinated plantsin Britain and the Netherlands. Science 313:

351-354.

Bhattacharya, M., R.B. Primack, and J. Gerwein. 2003. Are roads and railroads barriersto bumblebee movement in a temperate suburban

conservation area? Biological Conservation 109(1):37-45.

Black, S.H., N. Hodges, M. Vaughan, and M. Shepherd. 2007. Pollinatorsin natural areas: a primer on habitat management. The Xerces

Society, Portland, OR. Available: http://www.xerces.org/pollinators-in-natural-areas-a-primer-on-habitat-management/

Blake, R.J., D.B. Westbury, B.A. Woodcock, P. Sutton, and S.G. Potts. 2011. Enhancing habitat to help the plight of the bumblebee. Pest

Management Science 67:377–379.

Brown, M.J.F., and R.J. Paxton. 2009. The conservation of bees: a global perspective. Apidologie 40(3):410-416.

Cameron, S., S. Jepsen, E. Spevak, J. Strange, M. Vaughan, J. Engler, and O. Byers. 2011a. North American bumble bee species

conservation planning workshop finalreport.IUCN/SSC Conservation Breeding Specialist Group, Apple Valley, MN.

Cameron, S.A., J.D. Lozier, J.P. Strange, J.B. Koch, N. Cordes, L.F. Solter, and T.L. Griswold. 2011b. Patterns of widespread decline in

North American bumble bees. Proceedings of the National Academy of Science (USA) doi/10.1073/pnas.1014743108.

Carvell, C. 2002. Habitat use and conservation of bumblebees(Bombus spp.) under different grasslands managementregimes. Biological

Conservation 103(1):33-49.
12 Conservation and Management of North American Bumble Bees 

Acknowledgments

We thank John S. Ascher, American Museum of Natural History, for comments on this manuscript, and Samuel W. Droege, Patuxent Wildlife Research Center, U.S. Geological Survey, and Leif Richardson, Vermont Fish and Wildlife Department, for providing

information on several species. 

Internet Resources

The Bee Genera of Eastern Canada.—A usefulreference for distinguishing the bee genera of eastern Canada.(http://www.biology.ualberta.ca/

bsc/ejournal/pgs_03/pgs_03.html)

Bombus Bumblebees of the World.—Williams(2008a) checklist of the species of the world.(http://www.nhm.ac.uk/research-curation/

research/projects/bombus/index.html)

Bug Guide.—A resource for bumble bee identification, images, and information.(http://bugguide.net/node/view/3077)

Bumble Bee Conservation.—Linksto many useful conservation documents, created by the Xerces Society.(http://www.xerces.org/

bumblebees/)

Bumblebee Pages.—General bumble bee information for beginners.(http://www.bumblebee.org/)

Guide to Bumble bees.—An online key most useful forspecies of the eastern U.S.(http://www.discoverlife.org/mp/20q?guide=Bumblebees)

Plants for Pollinators.—Recommendations on plantsthat will enhance pollinator populations.(http://plant-materials.nrcs.usda.gov/technical/

pollinators.html)

Pollinator Partnership.—Information on protecting pollinatorsthrough conservation, education, and research.(http://www.pollinator.org)

References Cited

Alston, D. G., and V.J. Tepedino. 2000. Direct and indirect effects of insecticides on native bees. Pages 4-1 – 4-4 in Grasshopperintegrated

pest management user handbook (Technical Bulletin No. 1809), edited by G.L. Cuningham and M.W. Sampson. United States Department

of Agriculture Animal and Plant Health Inspection Services, Washington, D.C.

Bertsch, A., M. Hrabé de Angelis, and G.K.H. Przemeck. 2010. A phylogenetic framework forthe North American bumble bee species of

the subgenus Bombus sensu stricto (Bombus affinis, B. franklini, B. moderatus, B. occidentalis & B. terricola) based on mitochondrial DNA

markers. Beiträge zur Entomologie 60:229-242.

Biesmeijer, J.C., S.P.M. Roberts, M. Reemer, R. Ohlemüller, M. Edwards, T. Peeters, A.P. Schaffers, S.G. Potts, R. Kleukers, C.D. Thomas,

J. Settele, and W.E. Kunin. 2006. Parallel declinesin pollinators and insect-pollinated plantsin Britain and the Netherlands. Science 313:

351-354.

Bhattacharya, M., R.B. Primack, and J. Gerwein. 2003. Are roads and railroads barriersto bumblebee movement in a temperate suburban

conservation area? Biological Conservation 109(1):37-45.

Black, S.H., N. Hodges, M. Vaughan, and M. Shepherd. 2007. Pollinatorsin natural areas: a primer on habitat management. The Xerces

Society, Portland, OR. Available: http://www.xerces.org/pollinators-in-natural-areas-a-primer-on-habitat-management/

Blake, R.J., D.B. Westbury, B.A. Woodcock, P. Sutton, and S.G. Potts. 2011. Enhancing habitat to help the plight of the bumblebee. Pest

Management Science 67:377–379.

Brown, M.J.F., and R.J. Paxton. 2009. The conservation of bees: a global perspective. Apidologie 40(3):410-416.

Cameron, S., S. Jepsen, E. Spevak, J. Strange, M. Vaughan, J. Engler, and O. Byers. 2011a. North American bumble bee species

conservation planning workshop finalreport.IUCN/SSC Conservation Breeding Specialist Group, Apple Valley, MN.

Cameron, S.A., J.D. Lozier, J.P. Strange, J.B. Koch, N. Cordes, L.F. Solter, and T.L. Griswold. 2011b. Patterns of widespread decline in

North American bumble bees. Proceedings of the National Academy of Science (USA) doi/10.1073/pnas.1014743108.

Carvell, C. 2002. Habitat use and conservation of bumblebees(Bombus spp.) under different grasslands managementregimes. Biological

Conservation 103(1):33-49.
Conservation and Management of North American Bumble Bees 

Hopwood, J.L. 2008. The contribution ofroadside grassland restorationsto native bee conservation. Biological Conservation 141(10):2632-

2640.

Kearns, C.A., and J.D. Thomson. 2001. The natural history of bumblebees, a sourcebook forinvestigations. University Press of Colorado,

Boulder, CO.

Kevan, P. 1974. Pollination, pesticides and environmental quality. BioScience 24(4):198-199.

Kleijn, D., and I. Raemakers. 2008. A retrospective analysis of pollen host plant use by stable and declining bumble bee species. Ecology

89:1811-1823.

Kluser, S., and P. Peduzzi. 2007. Global pollinator decline: A literature review. UNEP/GRID-Europe.

Laverty T.M., and L.D. Harder. 1988. The bumble bees of eastern Canada. Canadian Entomologist 120(11):965–987.

Losey, J.E., and M. Vaughan. 2006. The economic value of ecologicalservices provided by insects. Bioscience 56(4):311-323.

MacCulloch, B. 2007. Delaware native bee guide, farming for native bees in Delaware. Delaware Department of Agriculture, Dover, DE. 

Available: http://dda.delaware.gov/plantind/pollinator.shtml

Master, L., D. Faber-Langendoen, R. Bittman, G.A. Hammerson, B. Heidel, J. Nichols, L. Ramsay, and A. Tomaino. 2009. NatureServe

conservation status assessments: factorsfor assessing extinction risk. NatureServe, Arlington, VA. Available: http://www.natureserve.org/

publications/ConsStatusAssess_StatusFactors.pdf

Matteson, K.C., J.S. Ascher, and G.A. Langellotto. 2008. Bee richness and abundance in New York City urban gardens. Annals of the

Entomological Society of America 101(1):140-150.

Matteson, K. C., and G.A. Langellotto. 2009. Bumble bee abundance in New York City community gardens: implicationsfor urban

agriculture. Cities and the Environment 2(1):1-12. Available: http://escholarship.bc.edu/cate/vol2/iss1/5

McFrederick, Q.S., and G. LeBuhn. 2006. Are urban parksrefugesfor bumble bees Bombus spp.(Hymenoptera: Apidae)? Biological

Conservation 129(3):372-382.

Meeus,I., M.J.F. Brown, D.C. De Graaf, and G. Smagghe. 2011. Effects of invasive parasites on bumble bee declines. Conservation Biology

25:662–671.

Mitchell, T.B. 1962. Bees of the eastern United States.II. Technical Bulletin of the North Carolina Agricultural Experiment Station 152:1-

557.

Mommaerts,V., S. Reynders, J. Boulet, L. Besard, G. Sterk, and G. Smagghe. 2010. Risk assessment forside effects of neonicotinoids

against bumblebees with and without impairing foraging behavior. Ecotoxicology 19(1):207-215.

Mommaerts, V., G. Sterk, and G. Smagghe. 2006. Hazards and uptake of chitin synthesisinhibitorsin bumblebees Bombus terrestris. Pest

Management Science 62:752-758.

NatureServe. 2009. Digital distribution of the rusty-patched bumblebee (Bombus affinis), an important pollinator. NatureServe, Arlington,

VA.

Noordijk, J., K. Delille, A.P. Schaffers, and K.V. Sýkora. 2009. Optimizing grassland management for flower-visiting insectsin roadside

verges. Biological Conservation 142(10):2097-2103.

Öckinger, E., and H.G. Smith. 2007. Semi-natural grasslands as population sourcesfor pollinating insectsin agricultural landscapes. Journal

of Applied Ecology 44(1):50-59.

Otterstatter, M.C., and J.D. Thomson. 2008. Does pathogen spilloverfrom commercially reared bumble beesthreaten wild pollinators?

PLoS ONE 3(7): e2771. Available: http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=2464710&blobtype=pdf

Pyke, G.H. 1982. Local geographic distributions of bumblebees near Crested Butte, Colorado: competition and community structure.

Ecology 63(2):555-573.

14
Conservation and Management of North American Bumble Bees 

Hopwood, J.L. 2008. The contribution ofroadside grassland restorationsto native bee conservation. Biological Conservation 141(10):2632-

2640.

Kearns, C.A., and J.D. Thomson. 2001. The natural history of bumblebees, a sourcebook forinvestigations. University Press of Colorado,

Boulder, CO.

Kevan, P. 1974. Pollination, pesticides and environmental quality. BioScience 24(4):198-199.

Kleijn, D., and I. Raemakers. 2008. A retrospective analysis of pollen host plant use by stable and declining bumble bee species. Ecology

89:1811-1823.

Kluser, S., and P. Peduzzi. 2007. Global pollinator decline: A literature review. UNEP/GRID-Europe.

Laverty T.M., and L.D. Harder. 1988. The bumble bees of eastern Canada. Canadian Entomologist 120(11):965–987.

Losey, J.E., and M. Vaughan. 2006. The economic value of ecologicalservices provided by insects. Bioscience 56(4):311-323.

MacCulloch, B. 2007. Delaware native bee guide, farming for native bees in Delaware. Delaware Department of Agriculture, Dover, DE. 

Available: http://dda.delaware.gov/plantind/pollinator.shtml

Master, L., D. Faber-Langendoen, R. Bittman, G.A. Hammerson, B. Heidel, J. Nichols, L. Ramsay, and A. Tomaino. 2009. NatureServe

conservation status assessments: factorsfor assessing extinction risk. NatureServe, Arlington, VA. Available: http://www.natureserve.org/

publications/ConsStatusAssess_StatusFactors.pdf

Matteson, K.C., J.S. Ascher, and G.A. Langellotto. 2008. Bee richness and abundance in New York City urban gardens. Annals of the

Entomological Society of America 101(1):140-150.

Matteson, K. C., and G.A. Langellotto. 2009. Bumble bee abundance in New York City community gardens: implicationsfor urban

agriculture. Cities and the Environment 2(1):1-12. Available: http://escholarship.bc.edu/cate/vol2/iss1/5

McFrederick, Q.S., and G. LeBuhn. 2006. Are urban parksrefugesfor bumble bees Bombus spp.(Hymenoptera: Apidae)? Biological

Conservation 129(3):372-382.

Meeus,I., M.J.F. Brown, D.C. De Graaf, and G. Smagghe. 2011. Effects of invasive parasites on bumble bee declines. Conservation Biology

25:662–671.

Mitchell, T.B. 1962. Bees of the eastern United States.II. Technical Bulletin of the North Carolina Agricultural Experiment Station 152:1-

557.

Mommaerts,V., S. Reynders, J. Boulet, L. Besard, G. Sterk, and G. Smagghe. 2010. Risk assessment forside effects of neonicotinoids

against bumblebees with and without impairing foraging behavior. Ecotoxicology 19(1):207-215.

Mommaerts, V., G. Sterk, and G. Smagghe. 2006. Hazards and uptake of chitin synthesisinhibitorsin bumblebees Bombus terrestris. Pest

Management Science 62:752-758.

NatureServe. 2009. Digital distribution of the rusty-patched bumblebee (Bombus affinis), an important pollinator. NatureServe, Arlington,

VA.

Noordijk, J., K. Delille, A.P. Schaffers, and K.V. Sýkora. 2009. Optimizing grassland management for flower-visiting insectsin roadside

verges. Biological Conservation 142(10):2097-2103.

Öckinger, E., and H.G. Smith. 2007. Semi-natural grasslands as population sourcesfor pollinating insectsin agricultural landscapes. Journal

of Applied Ecology 44(1):50-59.

Otterstatter, M.C., and J.D. Thomson. 2008. Does pathogen spilloverfrom commercially reared bumble beesthreaten wild pollinators?

PLoS ONE 3(7): e2771. Available: http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=2464710&blobtype=pdf

Pyke, G.H. 1982. Local geographic distributions of bumblebees near Crested Butte, Colorado: competition and community structure.

Ecology 63(2):555-573.

14
16 Conservation and Management of North American Bumble Bees

Appendix – 

Conservation 

Status of North 

American 

Bumble 

Bees

Taxonomy follows Williams(2008a), except that we follow other authoritiesin

recognizing Bombus occidentalis as distinct from B. terricola (Thorp and Shepherd

2005, Rao and Stephan 2007). Mostspecies do not have English names. Rapidly declining species are indicated with an asterisk (*). Conservation statusis denoted by the NatureServe Grank scheme, where “G1”indicatesthe highest level of imperilment and “G5”the most

secure.“GU”indicatesthat information on current population size and distribution are not comprehensive enough to specify a rank, although all bumble bee species with this designation are declining. 

“Q” denotes a species of questionable taxonomic validity. A “?”indicateslower confidence in the rank.

Taxonomic notes.—The western North American form Bombus californicus, not recognized by Williams 

(2008a) and not listed here, is considered by some authoritiesto be distinct from B. fervidus. Taxonomists disagree 

over whether B. jonellus and B. lapponicus occur in North America, but we include these two species following Williams(2008a). We include B. moderatus (= B. lucorum complex of Williams 2008a, in part)following Bertsch et al.(2010).

We also omit the Eurasian B. distinguendus, which occurs on Attu Island, Alaska.

Scientific Name (subgenus) English Name Grank Range

Bombus (Alpinobombus) balteatus G5 Circumpolar, south to New Mexico

Bombus (Alpinobombus) hyperboreus G5 Circumpolar in high arctic

Bombus (Alpinobombus) neoboreus G4G5 Arctic regions of western Canada and Alaska

Bombus (Alpinobombus) polaris G5 Circumpolar in high arctic

Bombus (Bombias) auricomus Black and Gold Bumble Bee G4G5 Much of North America south of the arctic

Bombus (Bombias) nevadensis G4G5 Western North America

Bombus (Bombus) affinis* Rusty-patched Bumble Bee G1G2 East central North America (see Figure 3)

Bombus (Bombus) franklini* Franklin’s Bumble Bee G1 Southern Oregon to northern California

Bombus (Bombus) moderatus G5 Western Canada and Alaska

Bombus (Bombus) occidentalis* Western Bumble Bee G2G3 Western North America

Bombus (Bombus) terricola* Yellowbanded Bumble Bee G2G4 Southern Canada, northern U.S., and in mountains 

south to North Carolina

Bombus (Cullumanobombus) crotchii G3G4 Central California to Baja California del Norte, Mexico

Bombus (Cullumanobombus) fraternus Southern Plains Bumble Bee G4 Central and coastal plain of eastern U.S.

Bombus (Cullumanobombus) griseocollis Brown-belted Bumble Bee G5 Southern Canada and most of the U.S.

Bombus (Cullumanobombus) morrisoni Morrison’s Bumble Bee G4G5 Western North America

Bombus (Cullumanobombus) rufocinctus Red-belted Bumble Bee G4G5 Widespread in North American except for the 

southeastern U.S.

Bombus (Psithyrus) ashtoni* Ashton’s Cuckoo Bumble Bee GH Across northern North America

Bombus (Psithyrus) citrinus Lemon Cuckoo Bumble Bee G4G5 Eastern North America

Bombus (Psithyrus) fernaldae Fernald’s Cuckoo Bumble Bee GU Northern North America
16 Conservation and Management of North American Bumble Bees

Appendix – 

Conservation 

Status of North 

American 

Bumble 

Bees

Taxonomy follows Williams(2008a), except that we follow other authoritiesin

recognizing Bombus occidentalis as distinct from B. terricola (Thorp and Shepherd

2005, Rao and Stephan 2007). Mostspecies do not have English names. Rapidly declining species are indicated with an asterisk (*). Conservation statusis denoted by the NatureServe Grank scheme, where “G1”indicatesthe highest level of imperilment and “G5”the most

secure.“GU”indicatesthat information on current population size and distribution are not comprehensive enough to specify a rank, although all bumble bee species with this designation are declining. 

“Q” denotes a species of questionable taxonomic validity. A “?”indicateslower confidence in the rank.

Taxonomic notes.—The western North American form Bombus californicus, not recognized by Williams 

(2008a) and not listed here, is considered by some authoritiesto be distinct from B. fervidus. Taxonomists disagree 

over whether B. jonellus and B. lapponicus occur in North America, but we include these two species following Williams(2008a). We include B. moderatus (= B. lucorum complex of Williams 2008a, in part)following Bertsch et al.(2010).

We also omit the Eurasian B. distinguendus, which occurs on Attu Island, Alaska.

Scientific Name (subgenus) English Name Grank Range

Bombus (Alpinobombus) balteatus G5 Circumpolar, south to New Mexico

Bombus (Alpinobombus) hyperboreus G5 Circumpolar in high arctic

Bombus (Alpinobombus) neoboreus G4G5 Arctic regions of western Canada and Alaska

Bombus (Alpinobombus) polaris G5 Circumpolar in high arctic

Bombus (Bombias) auricomus Black and Gold Bumble Bee G4G5 Much of North America south of the arctic

Bombus (Bombias) nevadensis G4G5 Western North America

Bombus (Bombus) affinis* Rusty-patched Bumble Bee G1G2 East central North America (see Figure 3)

Bombus (Bombus) franklini* Franklin’s Bumble Bee G1 Southern Oregon to northern California

Bombus (Bombus) moderatus G5 Western Canada and Alaska

Bombus (Bombus) occidentalis* Western Bumble Bee G2G3 Western North America

Bombus (Bombus) terricola* Yellowbanded Bumble Bee G2G4 Southern Canada, northern U.S., and in mountains 

south to North Carolina

Bombus (Cullumanobombus) crotchii G3G4 Central California to Baja California del Norte, Mexico

Bombus (Cullumanobombus) fraternus Southern Plains Bumble Bee G4 Central and coastal plain of eastern U.S.

Bombus (Cullumanobombus) griseocollis Brown-belted Bumble Bee G5 Southern Canada and most of the U.S.

Bombus (Cullumanobombus) morrisoni Morrison’s Bumble Bee G4G5 Western North America

Bombus (Cullumanobombus) rufocinctus Red-belted Bumble Bee G4G5 Widespread in North American except for the 

southeastern U.S.

Bombus (Psithyrus) ashtoni* Ashton’s Cuckoo Bumble Bee GH Across northern North America

Bombus (Psithyrus) citrinus Lemon Cuckoo Bumble Bee G4G5 Eastern North America

Bombus (Psithyrus) fernaldae Fernald’s Cuckoo Bumble Bee GU Northern North America
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FS-991 February 2012

Front cover left, Bombus impatiens 

male, photo Sheila Colla.

Front cover right, bee aloft, 

photo Ron Panzer.

Back cover left, Bombus perplexus, 

photo Sheila Colla.