Bumble Bees of the Western United States - USDA Forest Service

Table of Contents3 Table of Contents4 Foreword5 About the Authors6 Introduction10–12 Bee Diagrams13–15 Methodology16–17 Measuring Face Characteristics and Color18 Species Guides (color coded)18–81 Long- or square-cheeked bees with a rounded angle on the mid leg82–109 Short-cheeked bees with a rounded angle on the mid leg110–125 Long-cheeked bees with a sharp angle on the mid leg126–137 Bees with hind leg outer tibial surface convex and uniformly hairy (cuckoo bumble bees)138 Identification Key142 Acknowledgements143 Web and Other ResourcesGuide toBumble Beesof theWesternUnited StatesBumble Bees of the Western United States 3

ForewordBumble bees are among the most important and conspicuousof native pollinators, both for wildflowers and agriculture,yet they are not well known by non-scientists. This is inpart because there have not been accessible field guidesfor identifying them. This situation was recently remediedfor the eastern U.S., with the publication of Bumble Beesof the Eastern United States. Now residents of the westernU.S. have access to a similarly valuable resource, with theappearance of this new guide to Bumble Bees of the WesternUnited States.Bumble bees have been the subject of many importantecological studies in the western U.S., including research onforaging behavior, floral resource competition, and pollination.They have also provided some of the first information abouthow altitudinal distributions of animals are changing due tothe changing climate (moving up hundreds of meters in theColorado Rocky Mountains since the 1970s). This guide willbe a valuable resource for scientists conducting these kinds ofresearch involving bumble bees.A growing audience for information about bumble bees arepeople interested in their value as pollinators of commercialcrops of fruits and vegetables, as well as backyard gardens.The information about the tongue length of each species mayhelp growers figure out what the most economically valuablespecies are for their particular crops, and the ability toidentify different species will help to develop appreciation forthem.The growing audience of people who are interested in naturalhistory will also find this guide a valuable resource. The abilityto identify bumble bees is a challenging skill to develop, but theinformation and photographs in the guide will help facilitate thisgoal. People who develop this skill will be valuable collaboratorsfor scientists seeking to refine our knowledge about thedistribution and abundance of bumble bees.Unfortunately several bumble bee species are also thesubject of concern by conservation biologists and growers.In California and Oregon, Bombus franklini may be on thebrink of extinction, while Bombus occidentalis is experiencingdramatic declines in abundance and range. This is mostlikely due to the introduction of some European parasites anddiseases during the international commercial trade in bumblebees for their use in greenhouse pollination of plants such astomatoes. This guide will hopefully help both non-scientistsand scientists track the distribution and abundance of theseimportant pollinators, providing valuable information abouttheir conservation status.David Inouye, Ph.D.Co-author of Techniques for Pollination Biologists,and a long-time bumble bee researcher4 Bumble Bees of the Western United States

Color plates of male bumble bees are provided, but hair colorationin males is not the most reliable character. Thus questionableidentifications of a male may require an expert as the mainmorphological differences are found on the male genitalia.HabitatWhile they are closely related to the non-native European honeybee (Apis mellifera), bumble bees do not produce commercialquantities of honey, and are used less often in commercial pollination.However, bumble bees are arguably more important in thepollination of native flowers in natural ecosystems of the UnitedStates, and have evolved in a broad array of habitats, from thePuget Sound in Washington to the deserts of the Southwest.As a genus, bumble bees inhabit temperate regions worldwideand several species are even known from the equatorial regionsof the Neotropics. However, bumble bees dominate the pollinationlandscape in northern climates. They are importantin boreal forests, cold prairies, coastal plains, and mountainhabitats. Their ability to survive in cold climates makes themthe primary pollinators of alpine flowering plants and some ofthe few organisms that can survive in an arctic environment orat high elevations where temperatures drop well below freezingin the winter.When looking for bumble bees it is best to go to where flowers areblooming. Do not expect to find a nest as they are often undergroundin abandoned rodent burrows; instead focus on bumblebees visiting flowers. In forested areas, we most commonly encounterbumble bees along stream courses, in meadows, recentlyBombus terarius foraging on Asteraceae.burned or logged areas, or on flowers by roadsides. Each differentmicro-habitat provides different resources and a greater chanceto encounter a new species of bumble bee. For example in CacheValley, Utah we find several species of bumble bees in the agriculturalfields at the valley floor (1400m or 4600’), another groupof species in the mountain canyons of the Cache National Forest(1500-2500m or 5000’-8000’) and a third group of species in thehigh meadows (above 2500m or 8000’). Furthermore, we find thattwo field sites at the same elevation located 1km apart can havevery different fauna if the flowering plants in bloom are different.Bumble Bees of the Western United States 7

DietBumble bees are generalist foragers, feeding on a diverse suite of pollenand nectar resources. In the course of foraging for floral resources for thenest, an individual bumble bee will move pollen within a plant (for self-fertileplants), or from one plant to another (for out-crossing plants), affectingpollination success. For the bumble bee this is incidental but ecologicallyimportant nonetheless. The bumble bee collects extra pollen and consumesnectar which it transports back to the nest to feed the developinglarval bees. A nearly constant supply of dietary resources is critical tocolony growth and development. In the laboratory a nest of 100 bumblebees will consume nearly 2g of pollen and over 40ml of sugar syrup a dayrequiring nearly constant foraging. The nests of some species have beenobserved to reach a size of over 1000 individuals, while other speciesrarely exceed 50 individuals. The available floral resources in a habitat willdetermine what type of bumble bee species can survive in an area as wellas the density of nests an ecosystem can support.Bumble bees are important pollinators of wild land plants and are theprimary pollinators for crops in greenhouses. Bumble bees are especiallyeffective at pollinating plants in the nightshade family (Solanaceae) whichincludes pepper, tomato, and eggplant. While these plants are self-fertile,they benefit from bumble bee visits which help release pollen within theflowers. In addition many berry (blueberry, cranberry, currant, and raspberry),fruit (apricot, apple, melon, and squash), and seed crops (alfalfa,clover, and onion) are benefitted by bumble bees.Bombus huntii foraging on Echinacea sp.8 Bumble Bees of the Western United States

Life CycleBumble bees are considered primitively eusocial because theyform colonies founded by a solitary queen in the spring of eachyear. A queen lives only one year, but some species can produceover a thousand offspring in that time. The solitary queen typicallyoverwinters in the ground in a small cavity she excavatedtermed a hibernaculum. As the snow melts and the soil warmsin the spring, the queen emerges and begins flying around lookingfor a nest site, while stopping to feed on nectar-producingflowers. Most bumble bees nest in the ground in cavities suchas abandoned rodent burrows, holes in building foundations,or stacks of firewood. Once the queen finds a suitable site, shewill begin preparing the nest space by building a small wax cup,called a honey pot, and collects pollen which she will use tofeed her developing brood. When the nest is sufficiently provisioned,she will lay eggs on the pollen lump and begin incubatingthe eggs by laying her abdomen over the brood to keep theeggs or larvae warm. At this point the queen remains in the nestunless she needs to collect more food. Nearly four weeks afterlaying the first eggs her first workers will emerge as adults andbegin the jobs of foraging, nest cleaning, and brood care. Thecolony will grow throughout the summer and the workers willhelp the queen produce a clutch of male offspring, followedsoon by new queen bees. These reproductive bees will leavethe nest and find mates. After mating, the males die and thequeens feed briefly before digging their individual hibernaculaand become dormant for the winter. Each species is a littledifferent in optimal colony conditions, the size of the colony,the number of new queens they produce, and the seasonality(phenology) of these events.Bees and AllergiesAbout 3% of adults are truly allergic to bee stings. For most ofthese people, a sting will result in hives, itching and swelling(not just at the sting site, but everywhere) and, rarely, anaphylacticshock. It is a good idea to keep an EpiPen® on hand ifyou are handling bumble bees. Most bee stings can be treatedwith ice and an antihistamine, if needed. For more informationabout ways to avoid stings, please visit http://www.pollinator.org/nappc/brochures.htm for the NAPPC publication No Fear!Bombus griseocollis nest.Bumble Bees of the Western United States 9

Bumble Bee Body Diagramthoraxheadantennafore legthoraxheadinner-alarspaceT1clypeuscompound eyeanterior scutumwing basescutellumwingsT1T2T3T4mid leghind legabdomenT2T3T4T5T6abdomen(withnumberedterga/ “T”)T5T6corbiculum/pollen basketBombus ternarius, queen10 Bumble Bees of the Western United States

Bumble Bee Hind Leg Diagramcoxafemurtrochantertibia(i.e. corbiculum or “pollen basket”)corbicular fringebasitarsustarsitibial spursDistal posterior corner (mid leg character)tarsal clawBumble Bees of the Western United States 11

Bumble Bee Face Diagramsupraorbital lineocellicompound eyeantennacheek (malar space)clypeusmandibleBombus balteatus, queen12 Bumble Bees of the Western United States

Map MethodologyThe maps produced for this guide provide two sets of information about the range of each bumble bee species: (1) points that representactual bumble bee collections within the past 100 years, and (2) generalized range polygons meant to inform the geographicextent of a bumble bee’s distribution in areas where we lack specimen collection data. Many natural history collections and individualshave contributed their digitized, georeferenced data to this effort, as well as curatorial expertise. The dots on each map representcollections held by the following:Jason Weintraub, Academy of Natural Sciences, Philadelphia Robbin Thorp and Steve Heydon, University of California, DavisJohn Ascher, American Museum of Natural HistoryDoug Yanega, University of California, RiversideShepherd Myer, Bernice Pauahi Bishop MuseumCrystal Boyd and Virginia Scott, University of Colorado, BoulderSean Clark and Kimberly Huntzinger, Brigham Young University Frank Merickel, University of IdahoNorm Penny and Vince Lee, California Academy of Sciences Michael Engel and Jennifer Thomas, University of KansasStephen Gaimari, California State Collection of Arthropods David Golick, University of NebraskaDavid Ward Jr. and William Clark, College of IdahoSteven Krauth, University of Wisconsin, MadisonMichael Rose and Michael Ivie, Montana State University Richard Zack, Washington State UniversityTerry Griswold and Harold Ikerd, National PollinatingLawrence Gall, Yale UniversityInsect Collection (USDA-ARS)Brian Brown, Natural History Museum of Los Angeles CountyJeff Knight, Nevada Department of Agriculture, Plant Industry DivisionChristopher Marshall, Oregon State Arthropod CollectionPamela Horsley and Michael Wall, San Diego Natural History MuseumElizabeth Elle, Simon Fraser UniversityDavid Furth and Sèan Brady, Smithsonian InstitutionPaul Johnson, South Dakota State UniversityCheryl Barr and Robert Zuparko, University of California, BerkeleyBumble Bees of the Western United States 13

Many other natural history collections exist that have not beendigitized or checked for identification accuracy. These maps canthus be improved as more data become available.Maps are at a scale of 1:12,000,000 using the WGS 1984datum and projected with the North American Lambert ConformalConic. For each species, a range polygon (shown in green)was produced by buffering specimen collection points (shownin yellow) by 100 kilometers, then merging all buffers together.This was chosen as an arbitrary distance from known locationsof occurrence (i.e. sites where specimens have been collected)because in general, it helps describe a bumble bee species’ absolutedistribution extent. Furthermore, unlike the eastern UnitedStates, the western United States has extreme topographic variation,particularly in the Intermountain West (e.g. Idaho, Nevada,Utah), thus limiting some bumble bee species like Bombusbalteatus to high elevation mountains. Considering the lack ofcollections and surveys in much of the west, the range polygonspresented in this guide will provide the reader with a general ideaof a bumble bee species’ distribution. Minor changes were madeto the resulting layer to connect adjacent polygons where wethought it appropriate, to smooth some edges, and to improve thepresentation of the map. The range polygon was then clipped tothe western United States. These decisions were based primarilyon maps developed by Thorp et al. (1983) Bumble Bees andCuckoo Bumble Bees of California and Stephen (1957) Bumblebees of Western America (Hymenoptera: Apoidea).Range information is shown for states west of the 100° longitudeline. As several species also occur in the eastern United StatesBombus vosnesenskii range map, as example of a map indicating range of species in green, specimencollection points in yellow.(e.g. Bombus fervidus), an inset map of the entire United Statesis also provided for each species as well. This map will providethe user with an idea on the patterns of bumble bee distribution.For species distributed in the eastern United States, please referto the complimentary eastern field guide Bumble Bees of theEastern United States by Sheila Colla, Leif Richardson, and PaulWilliams. Finally, bear in mind that several of the bumble beesdocumented in the western United States also occur in parts ofadjacent Canada and Mexico and as far north as Alaska; however,ranges outside the contiguous United States are not presented.14 Bumble Bees of the Western United States

Phenology MethodologyThe annual colony phenology of each bumble bee species isestimated with data captured from the USDA-ARS National PollinatingInsect Database (NPID). Seasonal phenology was calculatedby comparing the relative abundance of each caste withina single month of a specific geographic region and the monthlyrelative abundance was plotted onto a graph. As many westernbumble bees are distributed across a wide variety of latitudes andelevations, estimates of seasonal phenology in queens, workers,and males of a species were limited to the following states andcounties: (1) California = Madera, Mariposa, Mono, Siskiyou, andTuolumne; (2) Idaho = Latah; (3) Oregon = Jackson; (4) Washington= Clallam, Coos, King, Skagit, Snohomish, and Whitman; (5)Utah = Box Elder and Cache. For Bombus crotchii and Bombuspensylvanicus subsp. sonorus, all records found in California andB. vosnesenskii phenology - Tuolumne Co., CAMalesWorkersQueensArizona were utilized to estimate their seasonal phenology, respectively.Bombus frigidus phenology was calculated with datafrom Fairbanks-North Star Borough, Alaska due to the paucityof data points in the contiguous United States. These graphsare meant to show the relative phenology of the various speciesand considerable adjustments may need to be made dependingon the latitude and elevation where you are looking for a givenspecies.Floral ResourceMethodologyThe floral hosts presented in this field guide for each bumblebee species were selected by querying the USDA-ARS NPID.The six flower genera associated with each species were themost commonly associated genera in the NPID (i.e. the bumblebee was detected on the flower). However, as bumble bees arefloral generalist, the flowers you find them on will vary withthe time of year and the place you are searching for them. Forbumble bees that primarily occur in the eastern United Statessuch as Bombus terricola and Bombus vagans, the floral associationssuggested by Bumble Bees of the Eastern United Statesare maintained.Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus vosnesenskii phenology chart, as example of a chart indicating relative abundance of eachcaste throughout the year.Bumble Bees of the Western United States 15

Measuring the Supraorbital Line in Bumble BeesSupraorbital line isdepicted by dotted yellowline. For additionalreference to cheek(malar) length and ocellisee page 12 (BumbleBee Face Diagram)ocelli at supraorbital lineocelliocelli below supraorbital lineColor Characteristics in Bumble BeesPredominantly black hairsB. pensylvanicus subsp. sonorus16 Bumble Bees of the Western United StatesBlack and yellow hairs intermixed (cloudy)B. melanopygusPredominantly yellow hairsB. huntii

Measuring the Cheek (Malar) Length in Bumble BeesFront ViewShort Cheek Medium Cheek Long CheekSide ViewLengthWidthLength shorter Length equal Length longerthan width to width than wideBumble Bees of the Western United States 17

Bombus nevadensisNevada bumble bee• Status: Common• Select food plant genera: Astragalus, Balsamorhiza, Ceanothus,Cirsium, Helianthus, Melilotus, Ribes, Vicia• Tongue Length: Long• Distribution: Pacific coastline east to the Plains States,from Mexico to Canada; occurs across a variety ofenvironmental gradients• Can be confused with B. griseocollis and B. morrisoniB. nevadensis phenology - Cache Co., UTMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus nevadensis queen.Photo Leah Lewis18 Bumble Bees of the Western United States

Bombus nevadensis continued20 Bumble Bees of the Western United States

Bombus balteatusHigh country bumble bee• Status: Rare• Select food plant genera: Chamerion (Epilobium), Mertensia,Aster, Castilleja, Penstemon, Geranium• Tongue Length: Long• Distribution: Found in high latitude regions of Alaska and Canada;in the contiguous U.S. it is associated with high elevation sites ofColorado, Wyoming, Montana, and California• Can be confused with B. frigidusB. balteatus phenology - Tuolumne Co., CAMalesBombus balteatus worker.Photo Diane WilsonWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec22 Bumble Bees of the Western United States

Bombus balteatus continuedLateral image of Bombus balteatus queen.Photo Jonathan KochFace of Bombus balteatus queen.Photo Jonathan KochBumble Bees of the Western United States 23

Bombus balteatus continued24 Bumble Bees of the Western United States

Bombus caliginosusObscure bumble bee• Status: Uncommon• Select food plant genera: Baccharis, Cirsium, Lupinus, Lotus,Grindelia, Phacelia• Tongue Length: Medium• Distribution: Coastal areas from northern Washington tosouthern California• Easily confused for B. vosnesenskii or B. vandykeiB. caliginosus phenology - Western OregonMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus caliginosus foraging for pollen.Photo Armen Armaghanyan26 Bumble Bees of the Western United States

Bombus caliginosus continuedLateral image of Bombus caliginosus female.Photo Jonathan KochFace of Bombus caliginosus female.Photo Jonathan KochBumble Bees of the Western United States 27

Bombus caliginosus continued28 Bumble Bees of the Western United States

Bombus caliginosus continuedFemales (queens and workers, colors refer to ‘hair’)• Thorax anterior to black band between wing basesyellow, scutellum black, T1-3 black, T4 yellow, T5 andT6 black, S3* and S4 with long yellow hairs apically,face square.• Mid leg basitarsus with the distal posterior cornerrounded. Cheek length as long as broad. Hair of theface and top of head yellow. On the side of the thorax,the lower anterior surface with predominantly blackhair, corbicular fringes black. Hair length medium anduneven.*S refers to the sternites of the bumble bee, whichare found on the ventral side of the abdomen. Theyare analogous to the tergites (i.e. “T”) that are foundon the dorsal side of the abdomen. Therefore S3translates to “sternite 3”. See page 26 for an exampleof this color character.Bumble Bees of the Western United States 29

Bombus vandykeivan Dyke bumble bee• Status: Uncommon• Select food plant genera: Phacelia, Collinsia, Clarkia,Streptanthus, Penstemon, Stachys• Tongue Length: Medium• Distribution: Pacific States from Washington tosouthern California• Can be confused with B. vosnesenskii, B. caliginosus,and B. californicusB. vandykei phenology - Tuolomne Co., CAMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus vandykei.Photo James Strange30 Bumble Bees of the Western United States

Bombus vandykei continuedLateral image of Bombus vandykei female.Photo Jonathan KochFace of Bombus vandykei female.Photo Jonathan KochBumble Bees of the Western United States 31

Bombus vandykei continued32 Bumble Bees of the Western United States

Bombus vandykei continuedFemales (queens and workers, colors refer to ‘hair’)• Thorax anterior to distinct black band between wingbases yellow, scutellum and T1-2 usually black, T3yellow at least apically, T4-6 black.• Mid leg basitarsus with the distal posterior cornerrounded. Cheek length longer than broad. Hair of theface and top of head completely yellow. On the sideof the thorax, the lower anterior surface with blackhair, corbicular fringes black. S2-5* with yellow hairapically. Hair length medium and uneven.*Refer to page 29 for an explanation of thismorphological feature.Bumble Bees of the Western United States 33

Bombus centralisCentral bumble bee• Status: Common• Select food plant genera: Cirsium, Phacelia, Penstemon,Allium, Symphoricarpos, Monarda• Tongue Length: Long• Distribution: Sierra-Cascade Crest east to the Colorado RockyMountains and south into the high mountains of New Mexicoand Arizona• Can be confused with B. flavifronsB. centralis phenology - Cache Co., UTMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus centralis male.Photo Leah Lewis34 Bumble Bees of the Western United States

Bombus centralis continuedLateral image of Bombus centralis female.Photo Jonathan KochFace of Bombus centralis worker.Photo Jonathan KochBombus centralis queen.Photo James StrangeBumble Bees of the Western United States 35

Bombus centralis continued36 Bumble Bees of the Western United States

Bombus centralis continuedFemales (queens and workers, colors refer to ‘hair’)• Thorax anterior to distinct black band between wingbases yellow, scutellum and T1-2 yellow, T3-4 orange,T5 black, face long.• Mid leg basitarsus with the distal posterior cornerrounded. Cheek length longer than broad. Hair of theface and top of head predominantly yellow. On theside of the thorax, the lower anterior surface with long,predominantly yellow hair, corbicular fringes black withred admixture along posterior margin. Hair length long.Bumble Bees of the Western United States 37

Bombus sitkensisSitka bumble bee• Status: Common• Select food plant genera: Ebilobium, Lupinus, Rubus, Rosa,Vicia, Rhododendron• Tongue Length: Medium• Distribution: Almost exclusive to Pacific coastline in the U.S.except for populations found in the Sawtooth wilderness ofnorthern Idaho• Can be confused with B. flavifrons, B. mixtus, andB. melanopygusB. sitkensis phenology - Puget Sound, WAMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus sitkensis.Photo James Strange38 Bumble Bees of the Western United States

Bombus sitkensis continuedLateral image of Bombus sitkensis female.Photo Jonathan KochFace of Bombus sitkensis female.Photo Jonathan KochBombus sitkensis worker on daisy.Photo Don RolfsBombus sitkensis.Photo James StrangeBumble Bees of the Western United States 39

Bombus sitkensis continued40 Bumble Bees of the Western United States

Bombus sitkensis continuedFemales (queens and workers, colors refer to ‘hair’)• Thorax anterior to the wing bases black and yellowintermixed (clouded), scutellum black, sometimes withyellow/white intermixed laterally, T1-2 yellow, T3 black,T4-5 with pale hairs, face square.• Mid leg basitarsus with the distal posterior cornerrounded. Cheek length longer than broad. Hair of theface and top of head with black and yellow intermixed,ocelli large and at supraorbital line. On the side of thethorax, the lower anterior surface with black and yellowintermixed (cloudy). Corbicular fringes long and withyellowish-red hairs. Hair length medium and uneven.Bumble Bees of the Western United States 41

Bombus flavifronsYellow head bumble bee• Status: Common• Select food plant genera: Epilobium, Vicia, Trifolium,Penstemon, Geranium, Lathyrus• Tongue Length: Long• Distribution: Pacific coastline west to the Colorado RockyMountains, associated primarily with high elevations in theIntermountain West; dark form (B. flavifrons dimidiatus) found inwestern portions of the range; red form (B. flavifrons flavifrons)in eastern portions of the range• Can be confused with B. centralis and B. sitkensisB. flavifrons phenology - Cache Co., UTMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus flavifrons worker.Photo Elizabeth Elle42 Bumble Bees of the Western United States

Bombus flavifrons continuedLateral image of Bombus flavifrons female.Photo Jonathan KochFace of Bombus flavifrons female.Photo Jonathan KochBombus flavifrons worker.Photo Diane WilsonBumble Bees of the Western United States 43

Bombus flavifrons continued44 Bumble Bees of the Western United States

Bombus flavifrons continuedFemales (queens and workers, colors refer to ‘hair’)• Thorax with black and yellow hair intermixedespecially anteriorly, T1-2 yellow at leastapicolaterally, T3-4 red or black, T5 blacksometimes with yellow apically.• Mid leg basitarsus with the distal posteriorcorner rounded. Cheek length longer than broad.Hair of the face and top of head with black andyellow intermixed. On the side of the thorax, thelower anterior surface with long yellow hairs,corbicular fringes black with red admixturealong posterior margin. Hair length long anduneven.Bumble Bees of the Western United States 45

Bombus frigidusFrigid bumble bee• Status: Rare• Select food plant genera: Chamerion, Lupinus, Geranium,Symphoricarpos, Trifolium, Achillea• Tongue Length: Medium• Distribution: Northern Intermountain West and high elevationRockies; few records in eastern U.S.• Can be confused with B. mixtus and B. balteatusB. frigidus phenology - Fairbanks-North Star Bo., AKMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus frigidus worker on Senecio sp.Photo Jessica Forrest46 Bumble Bees of the Western United States

Bombus frigidus continuedLateral image of Bombus frigidus female.Photo Jonathan KochFace of Bombus frigidus female.Photo Jonathan KochBombus frigidus worker.Photo Diane WilsonBumble Bees of the Western United States 47

Bombus frigidus continued48 Bumble Bees of the Western United States

Bombus frigidus continuedFemales (queens and workers, colors refer to ‘hair’)• Thorax and T1-2 predominantly yellow, with ablack band between the wing bases, sides of thethorax yellow, T4 orange at least apically, T5 orangeoccasionally faded to yellow.• Mid leg basitarsus with the distal posterior cornerrounded. Cheek as long as broad. Hair of the faceblack or with some yellow hairs, corbicular fringesextensively pale orange. T2 anterio-laterally withoutscattered black hairs intermixed. Hair length long.Bumble Bees of the Western United States 49

Bombus vagansHalf-black bumble bee• Status: Common• Select food plant genera: Penstemon, Asclepias, Aster,Cirsium, Eupatorium, Spirea• Tongue Length: Medium• Distribution: Eastern Washington east to New Englandprimarily in states bordering Canada• Can be confused with B. flavifrons or B. rufocinctusB. vagans phenology - Whitman Co., WAMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecA worker Bombus vagans visits red clover.Photo Leif Richardson50 Bumble Bees of the Western United States

Bombus vagans continued52 Bumble Bees of the Western United States

Bombus vagans continuedFemales (queens and workers, colors refer to ‘hair’)• Thorax and T1 predominately yellow, sometimes with ablack spot between the wing bases, T2 predominatelyyellow at least anteriorly, T3-6 black, face long.• Mid leg basitarsus with the distal posterior cornerrounded. Cheek length slightly longer than broad,clypeus strongly swollen in the dorsal half, hindbasitarsus with the posterior margin strongly andevenly arched. Hair of the head black or with aminority of short pale hairs intermixed. Hair lengthshort and even.Bumble Bees of the Western United States 53

Bombus ternariusTri-colored bumble bee• Status: Common in the eastern U.S. but rare in the western U.S.• Select food plant genera: Trifolium, Tanacetum, Chrysothamnus,Monarda, Achillea, Eriogonum• Tongue Length: Medium• Distribution: Eastern Montana and Black Hills east to New England• Can be confused with B. rufocinctus, B. huntii, and B. bifariusB. ternarius phenology - South DakotaMalesWorkersBombus ternarius worker.Photo Nolie SchneiderQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec54 Bumble Bees of the Western United States

Bombus ternarius continuedLateral image of Bombus ternarius female.Photo Jonathan KochFace of Bombus ternarius female.Photo Jonathan KochBombus ternarius worker.Photo Gord HarrisonBombus ternarius worker.Photo Beatriz MoissetBumble Bees of the Western United States 55

Bombus ternarius continued56 Bumble Bees of the Western United States

Bombus ternarius continuedFemales (queens and workers, colors refer to ‘hair’)• Thorax and T1 predominantly yellow, with a black bandbetween the wing bases extending posteriorly in themiddle of the scutellum, T2-3 orange, T4 yellow, T5black, face round.• Mid leg basitarsus with the distal posterior cornerrounded. Cheek very slightly shorter than broad.Hair of face and top of the head black with patchesof yellow, or sometimes with black more extensivelyintermixed especially for workers, thoracic anteriorband usually yellow without black hairs intermixedexcept in some workers, which have the anteriormargin of the black band between the wing basesalways sharply defined, scutellum with yellow patchesentirely divided by a black posteriorly directed triangle,T2 red, at most with a few black hairs anteriomedially,T4 yellow, T5 black. Hair length short and even.Bumble Bees of the Western United States 57

Bombus mixtusFuzzy-horned bumble bee• Status: Common• Select food plant genera: Rubus, Symphoricarpos, Trifolium,Lupinus, Senecio, Epilobium• Tongue Length: Medium• Distribution: Pacific coast, east to the Colorado RockyMountains; north to Alaska; primarily associated with highelevations and northern latitudes• Can be confused with B. frigidusB. mixtus phenology - King Co., WAMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus mixtus female.Photo Armen Armaghanyan58 Bumble Bees of the Western United States

Bombus mixtus continuedLateral image of Bombus mixtus female.Photo Jonathan KochFace of Bombus mixtus female.Photo Jonathan KochBombus mixtus male on Gaultheria sp.Photo Don RolfsBombus mixtus male.Photo Don RolfsBumble Bees of the Western United States 59

Bombus mixtus continued60 Bumble Bees of the Western United States

Bombus melanopygusBlack tail bumble bee• Status: Common• Select food plant genera: Lupinus, Trifolium, Chamerion,Rubus, Senecio, Penstemon• Tongue Length: Medium• Distribution: Pacific coast east to the Colorado Rocky Mountains;dark color form (B. melanopygus edwardsii) found primarilyin California and southern Oregon; red form (B. melanopygusmelanopygus) found to the north and east• Can be confused with B. sylvicola, B. bifarius,B. rufocinctus, and B. huntiiB. melanopygus phenology - King Co., WAMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus melanopygus worker on Gaultheria sp.Photo Don Rolfs62 Bumble Bees of the Western United States

Bombus melanopygus continuedLateral image of Bombus melanopygus female.Photo Jonathan KochFace of Bombus melanopygus female.Photo Jonathan KochBombus melanopygus worker.Photo Elizabeth ElleBumble Bees of the Western United States 63

Bombus melanopygus continued64 Bumble Bees of the Western United States

Bombus huntii continued68 Bumble Bees of the Western United States

Bombus huntii continuedFemales (queens and workers, colors refer to ‘hair’)• Thorax anterior to distinct black band between wingbases yellow, scutellum, T1 and T4 yellow, T2-3orange, T5 black.• Mid leg basitarsus with the distal posterior cornerrounded. Cheek length as long as broad. Hair of theface and top of head completely yellow. On the side ofthe thorax, the lower anterior surface with yellow hair,corbicular fringes black. Hair length medium and even.Bumble Bees of the Western United States 69

Bombus sylvicolaForest bumble bee• Status: Uncommon• Select food plant genera: Senecio, Chamerion, Lupinus,Melilotus, Arenaria, Raillardella• Tongue Length: Medium• Distribution: High mountains in the western U.S. includingthe Sierra Nevada, some “Sky Islands” in the Great Basinand the Rocky Mountains• Can be confused with B. melanopygus, B. bifarius, B. huntii,and B. rufocinctusB. sylvicola phenology - ColoradoMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus sylvicola male on Asteraceae.Photo Joyce Knoblett70 Bumble Bees of the Western United States

Bombus sylvicola continuedLateral image of Bombus sylvicola female.Photo Jonathan KochFace of Bombus sylvicola female.Photo Jonathan KochBombus sylvicola female.Photo Diane WilsonBumble Bees of the Western United States 71

Bombus sylvicola continued72 Bumble Bees of the Western United States

Bombus sylvicola continuedFemales (queens and workers, colors refer to‘hair’)• Thorax anterior to distinct black band betweenwing bases yellow, scutellum and T1 yellow,T2-3 orange or black, if black sometimesyellow medially, T4 usually yellow, T5 yellowat least apicolaterally, face square.• Mid leg basitarsus with the distal posteriorcorner rounded. Cheek length as long asbroad. Hair on the center of face yellow withblack admixture above the antennal bases.On the side of the thorax, the lower anteriorsurface with yellow hairs, corbicular fringesblack. Hair length long and very uneven.Bumble Bees of the Western United States 73

Bombus vosnesenskiiVosnesensky bumble bee• Status: Very common, possibly increasing in abundance• Select food plant genera: Lupinus, Cirsium, Eriogonum,Phacelia, Clarkia, Ericameria• Tongue Length: Medium• Distribution: Exclusive to costal California, Oregon andWashington east towards the Sierra-Cascade Crest;uncommon, but present in Nevada• Can be confused with B. caliginosus, B. occidentalis,and B. vandykeiB. vosnesenskii phenology - Tuolumne Co., CAMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus vosnesenskii worker on Agastache sp.Photo Lee Solter74 Bumble Bees of the Western United States

Bombus vosnesenskii continuedLateral image of Bombus vosnesenskii female.Photo Jonathan KochFace of Bombus vosnesenskii female.Photo Jonathan KochBombus vosnesenskii.Photo Armen ArmaghanyanBombus vosnesenskii on Delphinium.Photo Lee SolterBumble Bees of the Western United States 75

Bombus vosnesenskii continued76 Bumble Bees of the Western United States

Bombus vosnesenskii continuedFemales (queens and workers, colors refer to ‘hair’)• Thorax anterior to black band between wing basesyellow, scutellum black, T1-3 black, T4 yellow, T5 andT6 black, face square and yellow.• Mid leg basitarsus with the distal posterior cornerrounded. Cheek length as long as broad. Hair of theface and top of head yellow. On the side of the thorax,the lower anterior surface with long, predominantlyblack hair, corbicular fringes black. Hair lengthmedium and even.Bumble Bees of the Western United States 77

Bombus bifariusTwo form bumble bee• Status: Very common• Select food plant genera: Melilotus, Lupinus, Aster, Senecio,Chrysothamnus, Cirsium• Tongue Length: Medium• Distribution: From the Pacific coast to the Rocky Mountains;from Arizona to Alaska; a dark form (B. bifarius nearcticus) inthe north and west; a red form (B. bifarius bifarius) found inthe south and east of the range• Can be confused with B. huntii, B. melanopygus, B. mixtus,B. rufocinctus, and B. sylvicolaB. bifarius phenology - Cache Co., UTMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus bifarius.Photo Don Rolfs78 Bumble Bees of the Western United States

Bombus bifarius continuedLateral image of Bombus bifarius queen.Photo Jonathan KochFace of Bombus bifarius queen.Photo Jonathan KochBombus bifarius.Photo Don RolfsBombus bifarius queen onTaraxacum officinale.Photo David InoyueBombus bifarius worker on Lupinus sp.Photo Lee SolterBumble Bees of the Western United States 79

Bombus bifarius continued80 Bumble Bees of the Western United States

Bombus bifarius continuedFemales (queens and workers, colors refer to ‘hair’)• Thorax anterior to black band between wing basesyellow or white and sometimes cloudy in appearance,scutellum with pale or yellow patches entirely dividedby a black posteriorly directed triangle, T1 yellow orpale white, T2 and T3 completely black or red, orblack and red admixture, T4 yellow, T5 and T6 black.Face square.• Mid leg basitarsus with the distal posterior cornerrounded. Cheek length as long as broad. Hair ofthe face and top of head predominately yellow orpale sometimes with black admixture. On the sideof the thorax, the lower anterior surface with long,predominantly yellow, or pale yellow hair, corbicularfringes red. Hair length medium.Bumble Bees of the Western United States 81

Bombus crotchiiCrotch bumble bee• Status: Uncommon• Select food plant genera: Antirrhinum, Phacelia, Clarkia,Dendromecon, Eschscholzia, Eriogonum• Tongue Length: Medium• Distribution: Exclusive to coastal California east towards theSierra-Cascade Crest; less common in western Nevada• Can be confused with B. caliginosus, B. occidentalis,and B. vandykeiB. crotchii phenology - Southern CaliforniaMalesWorkersBombus crotchii male.Photo Native PlantsQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec82 Bumble Bees of the Western United States

Short-cheeked bees with arounded angle on the mid legBombus crotchii continuedLateral image of Bombus crotchii female.Photo Jonathan KochFace of Bombus crotchii female.Photo Jonathan KochBumble Bees of the Western United States 83

Bombus crotchii continued84 Bumble Bees of the Western United States

Bombus crotchii continuedFemales (queens and workers, colors refer to pileor ‘hair’)• Thorax anterior to black between wing basesyellow, scutellum black, T1 black at leastmedially, T2 predominantly yellow, T3-5 red orblack, face square.• Mid leg basitarus with the distal posterior cornerrounded. Cheek length as long as broad. Hair ofthe face and top of head black. On the side ofthe thorax, the lower anterior surface with longblack hairs, corbicular fringes black.Bumble Bees of the Western United States 85

Bombus rufocinctusRed-belted bumble bee• Status: Common• Select food plant genera: Cirsium, Melilotus, Arctium,Trifolium, Aster, Tanacetum• Tongue Length: Short• Distribution: Broadly distributed across the northern half ofthe U.S. and throughout the southern Rocky Mountainsand the Sierra Nevada• Highly variable coloration; can be confused withB. melanopygus, B. bifarius, B. huntii, and B. sylvicolaB. rufocinctus phenology - Cache Co., UTMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus rufocinctus red morph queen.Photo Leah Lewis86 Bumble Bees of the Western United States

Bombus rufocinctus continuedLateral image of Bombus rufocinctus female.Photo Jonathan KochFace of Bombus rufocinctus female.Photo Jonathan KochBombus rufocinctus queen on flower.Photo Leah LewisBumble Bees of the Western United States 87

Bombus rufocinctus continued88 Bumble Bees of the Western United States

Bombus rufocinctus continuedFemales (queens and workers,colors refer to ‘hair’)• Similar to many color patternsshown by both western andeastern North Americanbumble bees, but smallbodied, short haired and witha very short face.• Mid leg basitarsus withthe distal posterior cornerrounded. Cheek lengthdistinctly shorter than broad.Many other combinationsof these color patterns areknown, but the hair of T2 isalmost always with at leasta yellow crescent anteriorly(only rarely very muchreduced). Hind basitarsuswith the posterior marginevenly but not stronglyarched. Hair length short andeven, body size small.Bumble Bees of the Western United States 89

Bombus griseocollisBrown-belted bumble bee• Status: Common• Select food plant genera: Phacelia, Medicago, Cirsium,Helianthus, Trifolium, Dipsacus• Tongue Length: Medium• Distribution: Northeastern California and Cascade Crest eastto the northern Intermountain West and Rocky Mountains;broadly distributed in the eastern U.S.• Can be confused with B. morrisoniB. griseocollis phenology - Cache Co., UTMalesWorkersQueensBombus griseocollis.Photo Diane WilsonJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec90 Bumble Bees of the Western United States

Bombus griseocollis continuedLateral image of Bombus griseocollis female.Photo Jonathan KochFace of Bombus griseocollis female.Photo Jonathan KochBombus griseocollis female.Photo Andrew WilliamsA Bombus griseocollis workercaptured by a crab spider.Photo Sheila CollaBumble Bees of the Western United States 91

Bombus griseocollis continuedFemales (queens and workers, colorsrefer to ‘hair’)• Thorax and T1 predominantly yellow,or with a black spot between thewing bases, T2 with a yellow orbrown crescent anteriorly, tail black,hair short.• Mid leg basitarsus with the distalposterior corner rounded. Cheeklength distinctly shorter than broad,ocelli large. Hair of the face and ofthe top of the head black or with onlya few yellow hairs intermixed, blackthoracic spot between the wing basesoften very small and inconspicuousbut dense. Sometimes workershave the yellow on T2 extending forthree quarters of the length of T2and forming a W-shape. Hair lengthvery short and even, the metasomarectangular and slightly flattened.Bumble Bees of the Western United States 93

Bombus morrisoniMorrison bumble bee• Status: Common• Select food plant genera: Cirsium, Cleome, Helianthus,Lupinus, Chrysothamnus, Melilotus• Tongue Length: Short• Distribution: Sierra-Cascade Crest east to the IntermountainWest and to South Dakota and south into Mexico; associatedprimarily with arid environments• Can be confused with B. griseocollisB. morrisoni phenology - Cache Co., UTMalesWorkersQueensBombus morrisoni worker on Aconitum columbianum.Photo Hartmut WischJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec94 Bumble Bees of the Western United States

Bombus morrisoni continuedLateral image of Bombus morrisoni female.Photo Jonathan KochFace of Bombus morrisoni female.Photo Jonathan KochBombus morrisoni.Photo James StrangeBumble Bees of the Western United States 95

Bombus morrisoni continuedFemales (queens and workers, colors refer to ‘hair’)• Thorax and T1-2 yellow, T3 yellow at least medially,T4-5 predominantly black, face round.• Mid leg basitarsus with the distal posterior cornerrounded. Cheek length distinctly shorter than broad.Hair of the face black and top of head yellow. On theside of the thorax, the lower anterior surface withmedium black hair, corbicular fringes black. Hairlength short and even.Bumble Bees of the Western United States 97

Bombus frankliniFranklin bumble bee• Status: Rare, possibly extinct; last detected in 2006• Select food plant genera: Ceanothus, Centaurea, Eriogonum,Lupinus, Trifolium, Veratrum• Tongue Length: Short• Distribution: Restricted to Klamath Mountains of southernOregon and northern California• Can be confused with B. occidentalis or B. vosnesenskii• Possibly the most narrowly distributed bumble bee in the worldB franklini phenology - OregonMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus franklini female.Photo James Strange98 Bumble Bees of the Western United States

Bombus franklini continuedLateral image of Bombus franklini.Photo Jonathan KochFace of Bombus franklini.Photo Jonathan KochBumble Bees of the Western United States 99

Bombus franklini continued100 Bumble Bees of the Western United States

Bombus franklini continuedFemales (queens and workers, colors refer to ‘hair’)• Yellow hair on thorax extending posteriorly beyond wingbases (U-shaped), scutellum and T1-4 black, T5 blackwith white hairs at least on extreme lateral margins.• Mid leg basitarsus with the distal posterior cornerrounded. Cheek length distinctly shorter than broad.Hair on the center of face yellow. On the side of thethorax, the lower anterior surface with predominantlyblack hair, corbicular fringes black. Hair length shortand even.Bumble Bees of the Western United States 101

Bombus occidentalisWestern bumble bee• Status: Rare throughout much of its range; in decline but maybe locally common• Select food plant genera: Melilotus, Cirsium, Trifolium,Centaurea, Chrysothamnus, Eriogonum• Tongue Length: Short• Distribution: Historically from the Pacific coast to the ColoradoRocky Mountains; severe population decline west of the Sierra-Cascade Crest, but populations are known from the Great Basin,the Rocky Mountains and Alaska; several subspecies have beensuggested• Can be confused with B. crotchii, B. mixtus, and B. terricolaB. occidentalis phenology - Cache Co., UTMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus occidentalis worker nectar robbing Ipomopsis aggregata.Photo David Inouye102 Bumble Bees of the Western United States

Bombus occidentalis continuedLateral image of Bombus occidentalis female.Photo Jonathan KochFace of Bombus occidentalis female.Photo Jonathan KochBombus occidentalis worker on daisy.Photo Joyce KnobelttBumble Bees of the Western United States 103

Bombus occidentalis continued104 Bumble Bees of the Western United States

Bombus occidentalis continuedFemales (queens and workers, colors refer to‘hair’)• Thorax anterior to black band between wingbases yellow, scutellum black or yellow, T1black, T2 and T3 black or yellow, T4 oftenwhite at least apicolaterally, T5 white, faceround.• Mid leg basitarsus with the distal posteriorcorner rounded. Cheek length slightlyshorter than width. Hair of the face and topof head predominately black with yellowsometimes intermixed. On the side of thethorax, the lower anterior surface withpredominantly black hair, sometimes withyellow intermixed, corbicular fringes red.Hair length medium and even.Bumble Bees of the Western United States 105

Bombus terricolaYellow-banded bumble bee• Status: Rare, declining since the mid 1990s• Select food plant genera: Vaccinium, Salix, Rosa, Rubus,Lonicera, Solidago, Aster• Tongue Length: Short• Distribution: Eastern Montana and the Black Hills east toNew England and throughout the Appalachian Mountains• Can be confused with B. pensylvanicus and B. occidentalisB. terricola phenology - Ransom Co., NDMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus terricola worker.Photo Leif Richardson106 Bumble Bees of the Western United States

Bombus terricola continuedLateral image of Bombus terricola female.Photo Jonathan KochFace of Bombus terricola female.Photo Jonathan KochBombus terricola male.Photo Leif RichardsonBombus terricola female.Photo Nelson DeBarrosBombus terricola worker.Photo Leif RichardsonBumble Bees of the Western United States 107

Bombus terricola continued108 Bumble Bees of the Western United States

Bombus terricola continuedFemales (queens and workers, colors refer to ‘hair’)• Thorax with yellow band(s), T1 black, T2-3 yellow, T4black, T5-6 black or yellow, face round.• Mid leg basitarsus with the distal posterior cornerrounded. Cheek length slightly shorter than broad,clypeus strongly swollen in the dorsal half, hindbasitarsus with the posterior margin strongly andevenly arched. Hair of the head black or with aminority of short pale hairs intermixed. Hair lengthshort and even.Bumble Bees of the Western United States 109

Bombus appositusWhite-shouldered bumble bee• Status: Common• Select food plant genera: Cirsium, Delphinium, Linaria,Trifolium, Geranium, Penstemon• Tongue Length: Long• Distribution: Abundant in higher elevations in the Cascades,Sierra Nevada, Intermountain West and Rocky Mountains; lessabundant in the coastal plains of Oregon and Washington• Can be confused with B. fervidusB. appositus phenology - Cache Co., UTMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus appositus worker on Delphinium sp.Photo Lee Solter110 Bumble Bees of the Western United States

Long-cheeked bees with asharp angle on the mid legBombus appositus continuedLateral image of Bombus appositus female.Photo Jonathan KochFace of Bombus appositus female.Photo Jonathan KochBombus appositus nest.Photo Leah LewisBumble Bees of the Western United States 111

Bombus appositus continued112 Bumble Bees of the Western United States

Bombus appositus continuedFemales (queens and workers, colors refer to ‘hair’)• Thorax anterior to black band between wing basespredominately white, scutellum yellow or occasionallywhite and T1-5 predominantly yellow or sometimesorange-brown, face long.• Mid leg basitarsus with the distal posterior cornersharply pointed (may be hidden by hair). Cheeklonger than broad. Hair of the face and top of headpredominately white or occasionally yellow. On theside of the thorax, the lower anterior surface withpredominantly black hair, corbicular fringes black. Hairlength short and even.Bumble Bees of the Western United States 113

Bombus californicusCalifornia bumble bee• Status: Uncommon, possibly in decline• Select food plant genera: Cirsium, Trifolium, Monardella,Astragalus, Penstemon, Abronia• Tongue Length: Long• Distribution: Dark form distributed throughout coastal California,Oregon and Washington; yellow form primarily distributedthroughout the Intermountain West and Rocky Mountains; bothforms co-occur in the Intermountain West along with B. fervidus,raising questions as to whether they are distinct species• Dark form can be confused with B. vosnesenskii,B. caliginosus, and B. vandykeiB. californicus phenology - Whitman Co., WAMalesWorkersQueensBombus californicus worker.Photo David InouyeJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec114 Bumble Bees of the Western United States

Bombus californicus continuedLateral image of Bombus californicus female.Photo Jonathan KochFace of Bombus californicus female.Photo Jonathan KochBombus californicus female.Photo Cheryl MooreheadBumble Bees of the Western United States 115

Bombus californicus continued116 Bumble Bees of the Western United States

Bombus californicus continuedFemales (queens and workers, colors refer to ‘hair’)• Thorax anterior to black band between wing basespredominately yellow, scutellum primarily black oroccasionally yellow intermixed, T1-3 predominantlyblack, especially for coastal specimens and may alsobe completely yellow except for small patches of blackon the apicolateral margins of T2 on specimens foundin the intermountain west and Colorado Rockies, T4always yellow, face long.• Mid leg basitarsus with the distal posterior cornersharply pointed (may be hidden by hair). Cheeklonger than broad. Hair of the face and top ofhead predominantly black with yellow sometimesintermixed. On the side of the thorax, the loweranterior surface predominantly black, sometimes withyellow intermixed, corbicular fringes black. Hair lengthshort and even. Yellow B. californicus males can beextremely hard to distinguish from B. fervidus males.Bumble Bees of the Western United States 117

Bombus fervidusYellow bumble bee• Status: Common in the western U.S., possibly declining inthe eastern U.S.• Select food plant genera: Cirsium, Penstemon, Phacelia,Helianthus, Dipsacus, Trifolium• Tongue Length: Long• Distribution: Found throughout most of the continental U.S.except for west of the Sierra-Cascade Crest; may be conspecificwith B. californicus• Can be confused with the yellow form of B. californicusas well as B. appositusB. fervidus phenology - Cache Co., UTMalesWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus fervidus queen.Photo Leah Lewis118 Bumble Bees of the Western United States

Bombus fervidus continuedLateral image of Bombus fervidus queen.Photo Jonathan KochFace of Bombus fervidus queen.Photo Jonathan KochBombus fervidus male.Photo Lloyd and Sandy SpitainikBumble Bees of the Western United States 119

Bombus fervidus continued120 Bumble Bees of the Western United States

Bombus fervidus continuedFemales (queens and workers, colors refer to ‘hair’)• Thorax anterior to black band between wing basesyellow, scutellum and T1-4 completely yellow, T5black, face long.• Mid leg basitarsus with the distal posterior cornersharply pointed (may be hidden by hair). Cheeklonger than broad. Hair of the face and top of headpredominantly black with yellow sometimes intermixed.On the side of the thorax, the lower anterior surfacepredominantly yellow, corbicular fringes black. Hairlength short and even.Bumble Bees of the Western United States 121

Bombus pensylvanicus subsp. sonorusSonoran bumble bee• Status: Uncommon• Select food plant genera: Gossypium, Viguiera, Helianthus,Linaria, Chrysothamnus, Kallstroemia• Tongue Length: Long• Distribution: California central valley south to Baja Californiaand east to western Texas• Can be confused with the yellow form B. crotchii andB. nevadensisB. pensylvanicus sonorus phenology - ArizonaMalesBombus pensylvanicus sonorus.Photo Racquel MorrisWorkersQueensJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec122 Bumble Bees of the Western United States

Bombus pensylvanicus subsp. sonorus continuedLateral image of Bombus pensylvanicus sonorus female.Photo Jonathan KochFace of Bombus pensylvanicus sonorus female.Photo Jonathan KochBombus pensylvanicus sonorus.Photo Ron HembergerBumble Bees of the Western United States 123

Bombus pensylvanicus subsp. sonorus continued124 Bumble Bees of the Western United States

Bombus pensylvanicus subsp. sonorus continuedFemales (queens and workers, colors refer to ‘hair’)• Thorax predominantly yellow with black usuallybetween wing bases, T1-3 yellow, T4-5 black, facelong.• Mid leg basitarsus with the distal posterior cornersharply pointed (may be hidden by hair). Cheeklonger than broad. Hair of the face and top of headpredominately black. On the side of the thorax, thelower anterior surface predominantly black, corbicularfringes black. Hair length short and even.Bumble Bees of the Western United States 125

Bombus insularisIndiscriminate cuckoo bumble bee• Status: Common• Select food plant genera: Erigeron, Solidago, Aster, Wyethia,Senecio, Trifolium• Tongue Length: Short• Hosts: B. rufocinctus, B. ternarius, B. terricola, B. occidentalis,B. nevadensis, B. californicus, and B. appositus• Distribution: Pacific coast east to New England; primarily instates bordering Canada• Can be confused with B. fernaldaeB. insularis phenology - Cache Co., UTMalesFemalesJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecFemale Bombus insularis.Photo Sheila Colla126 Bumble Bees of the Western United States

Bees with hind leg outer tibial surfaceconvex and uniformly hairy (cuckoo bumble bees)Bombus insularis continuedLateral image of Bombus insularis female.Photo Jonathan KochFace of Bombus insularis female.Photo Jonathan KochBombus insularis.Photo James StrangeBumble Bees of the Western United States 127

Bombus insularis continued128 Bumble Bees of the Western United States

Bombus insularis continuedFemales (no workers, colors refer to ‘hair’)• Face yellow, a black band between the wingbases, tail with some yellow.• Hind tibia with outer surface convex anddensely hairy. Hair of the face with a denseyellow patch above the base of the antenna,sometimes some yellow below the base ofthe antenna but predominantly black, blackhair forming a band between the wing bases,sides of the thorax yellow anteriorly but blackventrally and posteriorly, T3 usually withblack hair along the entire midline but yellowlaterally, T4 extensively yellow laterally. Wingslight brown.Bumble Bees of the Western United States 129

Bombus fernaldaeFernald cuckoo bumble bee• Status: Uncommon• Select food plant genera: Aster, Senecio, Potentilla, Trifolium,Chamaebatia, Cirsium• Tongue Length: Short• Hosts: B. rufocinctus• Distribution: Pacific coast east to New England• Can be confused with B. insularisB. fernaldae phenology - UTMalesBombus fernaldae female.Photo Beatriz MoissetFemalesJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec130 Bumble Bees of the Western United States

Bombus fernaldae continuedLateral image of Bombus fernaldae female.Photo Jonathan KochFace of Bombus fernaldae female.Photo Jonathan KochBumble Bees of the Western United States 131

Bombus fernaldae continued132 Bumble Bees of the Western United States

Bombus fernaldae continuedFemales (no workers, colors refer to ‘hair’)• Face black, top of head yellow orcream, T1 often black, yellow in theeast, T2 black, T3 black or yellow, T4yellow or cream, T5 black.• Hind tibia with outer surface convexand densely hairy. Hair of the faceblack. T6 curled very strongly underthe abdomen and pointing anteriorly,S6 ending distally with a shinytriangular spine, the lateral keelssmall. Hair long and uneven.Bumble Bees of the Western United States 133

Bombus suckleyiSuckley cuckoo bumble bee• Status: Uncommon• Select food plant genera: Aster, Centaurea, Cirsium, Trifolium,Chrysothamnus, Helichrysum• Hosts: B. occidentalis• Distribution: Pacific coast east to Nebraska; from New Mexiconorth to Alaska• Can be confused with B. insularis and B. fernaldaeB. suckleyi phenology - Cache Co., UTMalesFemalesJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecBombus suckleyi queen.Photo David Inouye134 Bumble Bees of the Western United States

Bombus suckleyi continuedLateral image of Bombus suckleyi female.Photo Jonathan KochFace of Bombus suckleyi female.Photo Jonathan KochBumble Bees of the Western United States 135

Bombus suckleyi continued136 Bumble Bees of the Western United States

Bombus suckleyi continuedFemales (no workers, colors refer to ‘hair’)• Face black, top of head yellow or black, T1-2 black,T3-5 predominately yellow.• Hind tibia with outer surface convex and densely hairy.Hair of face black. Hair behind head predominatelyblack. T6 curled very strongly under abdomen andpointing anteriorly, S6 ending distally with a shinytriangular spine, the lateral keels large. Hair long anduneven.Bumble Bees of the Western United States 137

Identification Keyfor the female bumble beesof the Western United StatesThe following dichotomous key designedby Jonathan Koch and James Strangewill help you identify female bumblebees to species. Starting at the firstset of statements determine whichcharacteristics your specimen hasand move to the next appropriate set(numbered at the end of the statement).When in the field a loupe or hand lensmight be helpful when identifyingcharacteristics like cheek length (i.e. malarspace) and ocelli distances.1. Females; antennae with 10 flagellomeres; abdomen with 6visible tergites…2- Males; antennae with 11 flagellomeres; abdomen with 7visible tergites…no key provided2(1). Outer surface of hind tibia concave and shiny (Pollenbaskets present; social species)…3- Outer surface of hind tibia convex and hairy (Pollenbaskets absent; parasitic species)…343(2). T2 and T3 with red or orange hairs, sometimes with yellowhairs intermixed at least medially…4- T2 and/or T3 with yellow or black hair…94(3). Scutum anterior to wing bases with yellow and black hairsintermixed, giving cloudy appearance (see page 16)...B.melanopygus- Scutum anterior to wing bases with predominantly yellowor pale yellow hairs...55(4). Cheek length (i.e. malar space; see page 17) distinctlyshorter than width; face with predominantly blackhairs...B. rufocinctus138 Bumble Bees of the Western United States

- Cheek length equal to width; face with yellowhairs, at least centrally...66(5). Scutellum with yellow hairs only...B. huntii- Scutellum with yellow or pale yellow patchesof hair divided by a black posteriorly directedtriangle...77(6). T5 with yellow hairs on the lateral margins; facewith yellow hairs centrally...B. sylvicola- T5 with completely black hairs...88(7). T2 with black hairs at least medially...B. bifarius subsp. bifarius- T2 with completely black hairs...B. ternarius9(3). Cheek length longer than width...10- Cheek length as long as or shorter thanwidth...2310(9). Face with pale white or yellow hairs, sometimeswith black hairs intermixed, giving cloudyappearance (see page 16)...11- Face with predominantly black hairs...1711(10). Anterior scutum with dull yellow or whitish hairs;T1-4 with all yellow or brownish hairs...B. appositus- Anterior scutum with yellow hairs, sometimeswith black hairs intermixed; T1-4 with differentcombinations of hair color...1212(11). Scutellum and T1-2 with black hairs...13- Scutellum and T1-2 with yellow hairs...1413(12). T3 with yellow band of hairs; T4 usually withblack hairs...B. vandykei- T3 with black hairs only; T4 with yellow bandof hairs...B. caliginosus14(12). T5-6 with pale white hairs...B. sitkensis- T5-6 with black hairs...1515(14). T3-4 with black hairs...B. flavifrons subsp.dimidiatus- T3-4 with orange hairs...1616(15). Anterior scutum with black and yellow hairsintermixed, giving cloudy appearance (seepage 16)...B. flavifrons- Anterior scutum with predominantly yellowhairs...B. centralisBumble Bees of the Western United States 139

17(10). T5-6 with orange or pale orange hairs;distributed primarily in high elevations of theColorado Rockies, isolated populations found inthe Sierra Nevada Mountains, south of Tahoe...B. balteatus- T5-6 with black hairs; variable distributions inwestern United States...1818(17). T3 completely with black hairs...19- T3 with yellow hairs at least medially...2019(18). T4 with black hairs...B. vagans- T4 with yellow hairs...B. californicus20(18). Scutum strongly banded with black hairsbetween wing bases...21- Scutum not strongly banded, predominantlywith yellow hairs...B. nevadensis21(20). T4 with predominantly black hairs...B. pensylvanicus subsp. sonorus- T4 with predominantly yellow hairs...2222(21). T2 with predominantly yellow hairs...B. fervidus- T2 with yellow hairs and black hairsapicolaterally...B. californicus subsp.consanguineus23(9). Ocelli below supraorbital line (see page 16)...24- Ocelli at supraorbital line...2724(23). Scutellum and T1 with yellow hairs...25- Scutellum and T1 with black hairs...B. crotchii25(24). Integument of T1 and T2 dull; scutum andscutellum almost obscured with yellowhairs...26- Integument of T1 and T2 shiny; scutum andscutellum not completely obscured, much blackhair between the wing bases...B. rufocinctus26(25). T3 with hairs all black...B. griseocollis- T3 with yellow hairs at least basiomedially...B. morrisoni27(23). Cheek length distinctly shorter than width...28- Cheek length as long as width...3028(27). Face with completely yellow hairs; only found inSiskiyou County, California and Jackson County,Oregon...B. franklini140 Bumble Bees of the Western United States

- Face with black hairs, sometimes yellowintermixed centrally; broadly distributed in theUnited States...2929(28). T2 completely covered with yellow hairs; foundin the Black Hills of South Dakota...B. terricola- T2 with black hairs at least basally; broadlydistributed in western United States...B. occidentalis30(27). T1 with completely black hairs...B. vosnesenskii- T1 with completely yellow hairs...31- Anterior scutum with predominantly yellowhairs; distributed primarily at the highestelevations of the Colorado Rockies...B. frigidus34(2). Occiput with predominantly black hairs...B. suckleyi- Occiput with predominantly yellow hairs...3535(34). Face with predominantly black hairs aroundbases of antennae...B. fernaldae- Face with predominantly yellow hairs aroundbases of antennae...B. insularis31(30). T2 with predominantly black hairs...32- T2 with predominantly yellow hairs...3332(31). T5 with lots of yellow hairs on the lateralmargins...B. melanopygus- T5 with predominantly black hairs on thelateral margins...B. bifarius subsp. nearcticus33(31). Anterior scutum with black and yellow hairsintermixed, giving cloudy appearance;broadly distributed in western United States...B. mixtusBumble Bees of the Western United States 141

AcknowledgementsSpecial thanks to Dr. Larry Stritch, National Botanist, US ForestService and The National Fish and Wildlife Foundation, The USForest Service, and Dr. Elizabeth Sellers, National BiologicalInformation Infrastructure, US Geological Survey for providingtheir support for this guide. We gratefully acknowledge helpand valuable discussion from Laurie Davies Adams, MargueriteMeyer, Joyce Knoblett, Leah Lewis, Terry Griswold, Harold Ikerdand photograph providers.We also would like to thank Nicole Boehme, CamdenHunt, Sarah Clark, Victor Gonzalez, Byron Love and ArmenArmaghanyan for providing insightful comments, feedback andtechnical support on the species identification key.Additionally, we would especially like to thank the followingindividuals and institutions for use of their digitized naturalhistory collection data, both critical in constructing rangemaps and estimating phenology: John Ascher (AmericanMuseum of Natural History), Terry Griswold and Harold Ikerd(USDA-ARS National Pollinating Insect Collection), DougYanega (University of California, Riverside), Crystal Boyd andVirginia Scott (University of Colorado, Boulder), Michael Engeland Jennifer Thomas (University of Kansas) and LawrenceGall (Yale University). Databasing efforts by John Ascher,Doug Yanega and Terry Griswold are supported by the NationalScience Foundation.Funding for this project was provided by the PollinatorPartnership, the U.S. Forest Service and the National Fish andWildlife Foundation.142 Bumble Bees of the Western United States

Web and Other ResourcesFor additional copies of this publication, Bumble Bees of the Western United States, or for copies of the companionvolume, Bumble Bees of the Eastern United States, visit the Pollinator Partnership at www.pollinator.org/books.Downloadable page versions are available through the U.S. Forest Service athttp://www.fs.fed.us/wildflowers/pollinators/documents/BumbleBeeGuide2011.pdfDownloadable page versions also available at www.pollinator.org/books.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.htmlBumblebee Economics by B. Heinrich, Harvard University Press, 2004.Bumblebees by D.V. Alford, Davis-Poynter, London, 1974.Bumblebees: their behaviour and ecology by D. Goulson, Oxford University Press, 2003.Williams, P.H. & J.L. Osborne. 2009.Bumblebee vulnerability and conservation world-wide. Apidologie 40: 367-387. [Online]http://www.nhm.ac.uk/research-curation/research/projects/bombus/Williams&Osborne09_review.pdfPollinator Partnership www.pollinator.org for Bombus White PaperXerces Society for Invertebrate Conservation [Online]http://www.xerces.org/bumblebees/Discover Life Bumble Bee Key [Online]http://www.discoverlife.org/mp/20q?guide=BumblebeesBumble Bees of the Western United States 143

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs andactivities on the basis of race, color, national origin, age, disability, and where applicable,sex, marital status, familial status, parental status, religion, sexual orientation, geneticinformation, political beliefs, reprisal, or because all or part of an individual’s incomeis derived from any public assistance program. (Not all prohibited bases apply to allprograms.) Persons with disabilities who require alternative means for communication ofprogram information (Braille, large print, audiotape, etc.) should contact USDA’s TARGETCenter at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, writeUSDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington,D.C. 20250-9410, or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA isan equal opportunity provider and employer.© 2012 Pollinator Partnership

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