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Bombus franklini

(Frison, 1921)

Franklin Bumble Bee

G1Critically Imperiled Found in 75 roadless areas NatureServe Explorer →
G1Critically ImperiledGlobal Rank
Critically endangeredIUCN
HighThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.109927
Element CodeIIHYM24010
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryInvertebrate Animal
IUCNCritically endangered
Endemicendemic to a single nation
KingdomAnimalia
PhylumArthropoda
ClassInsecta
OrderHymenoptera
FamilyApidae
GenusBombus
Synonyms
Bombus (Bombus) franklini(Frison, 1921)
Other Common Names
Franklin's bumblebee (EN)
Concept Reference
Williams, P. H. 2008a. Bombus, bumblebees of the world. Static copy of web pages based on Williams, P.H. 1998. An annotated checklist of bumblebees with an analysis of patterns of description (Hymenoptera: Apidae, Bombini). Bulletin of the Natural History Museum (Entomology) 67:79-152. [website now defunct]
Taxonomic Comments
Subgenus: Bombus. Previously treated as conspecific with B. occidentalis by Milliron (1971).
Conservation Status
Rank MethodLegacy Rank calculation - Excel v3.1x
Review Date2019-06-24
Change Date2019-06-24
Edition Date2018-04-07
Edition AuthorsSchweitzer, D.F (2012); Richardson, L.L. (2018)
Threat ImpactHigh
Range Extent<100 square km (less than about 40 square miles)
Number of Occurrences1 - 5
Rank Reasons
This species has one of the smallest known range extents of any bumble bee globally. Despite focused, annual inventories by a taxonomic specialist (Robbin Thorp), this species has not been seen since 2006, when a single individual was observed. Surveys are continuing and biologists are hopeful that more extant sites will be discovered (Oregon Biodiversity Information Center and California Natural Diversity Database, pers. comm. 2019).
Range Extent Comments
This species is only known from southern Oregon to northern California between the Coast and Sierra-Cascade Ranges (Thorp 1983). It has one of the smallest known range extents of any bumble bee globally. Only a single individual was observed in 2006 despite intensive annual survey effort in its known range (Williams et al. 2014; Richardson unpublished).
Occurrences Comments
A single individual was observed in 2006.
Threat Impact Comments
The massive declines of several species in this subgenus, and possible extinction of this one, are probably primarily due to introduced pathogens (Colla et al., 2006, Winter et al., 2006, Otterstatter and Thomson, 2008, Federman, 2009), perhaps especially a very virulent strain of Nosema bombi and Crithidia bombi. The disappearance of B. franklini was very soon after a major outbreak of Nosema in commercial bumble bee hives in the area (Winter et al., 2006, Federman, 2009) which was so severe as to lead to the discontinuation of cultivation of the closely related B. (B.) occidentalis which was common and native in the range of B. (B.) franklini. While other factors such as habitat loss and insecticides could have been causing some level of decline, other than exotic pathogen spillover no known factor could plausibly have a caused a range-wide collapse of this species in five years or less along with continent-wide declines or disappearances of at least three recently common and widespread species in this subgenus in the USA over a period of about a decade or less--especially considering that other bumble bees are declining less severely, or are stable, or even documented as increasing.
Ecology & Habitat

Description

See Frison (1921). QUEENS AND WORKERS: metasomal terga two or three with pile yellow or black or with traces of ferruginous or orange pile. First metasomal terga with pile black. Metasomal tergum five and/or six and sometimes four, with pile pale ferruginous, pale yellow, light gray or white, vertex with pile predominantly yellow. Corbicular fringes black, metasomal tergum two with pile all black. MALES: eyes not protuberant. Ocelli placed well below supraorbital line; malar spaces less than half as long as broad; metasomal tergum seven with pile all black; metasomal terga one to four with pile all black; head as broad as long (Stephen 1957).

Habitat

Found in open grassy coastal prairies and coast range meadows (Williams et al. 2014).

Many terrestrial habitat-checkoffs are based on an analysis of occurrence data and land-cover data by Chesshire et al. (2023).

Ecology

Found flying in the herbaceous grasslands between 1400-4000' elevation. Activity spans the entire blooming season so they do not appear especially restricted to a particular host or flower.

Reproduction

Nests underground; males patrol circuits in search of mates (Williams et al. 2014).
Terrestrial Habitats
Forest - ConiferWoodland - ConiferGrassland/herbaceousSuburban/orchardUrban/edificarian
Other Nations (1)
United StatesN1
ProvinceRankNative
CaliforniaSHYes
OregonS1Yes
Threat Assessments
ThreatScopeSeverityTiming
2 - Agriculture & aquacultureUnknownUnknownModerate - low
2.1 - Annual & perennial non-timber cropsUnknownUnknownModerate - low
8 - Invasive & other problematic species, genes & diseasesPervasive - largeSerious or 31-70% pop. declineHigh (continuing)
8.1 - Invasive non-native/alien species/diseasesPervasive - largeSerious or 31-70% pop. declineHigh (continuing)
9 - PollutionUnknownUnknownHigh (continuing)
9.3 - Agricultural & forestry effluentsUnknownUnknownHigh (continuing)

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Roadless Areas (75)
California (45)
AreaForestAcres
BlackKlamath National Forest6,530
Blue Creek Rare ISix Rivers National Forest12,134
Bonanza KingShasta-Trinity National Forest16,402
BoulderKlamath National Forest435
Box CampKlamath National Forest858
Castle Crags AShasta-Trinity National Forest113
Castle Crags BShasta-Trinity National Forest1,619
Condrey Mtn.Klamath National Forest2,923
CrapoKlamath National Forest1,487
Cub (fs)Klamath National Forest135
Dog CreekShasta-Trinity National Forest5,001
East GirardShasta-Trinity National Forest27,894
Granite PeakShasta-Trinity National Forest122
GriderKlamath National Forest10,647
Indian CreekKlamath National Forest5,011
Jacobs (fs)Klamath National Forest577
JohnsonKlamath National Forest10,652
KangarooKlamath National Forest40,617
KellySix Rivers National Forest5,195
KelseyKlamath National Forest3,237
Lake EleanorShasta-Trinity National Forest397
Monkey CreekSix Rivers National Forest9,017
Mt. EddyShasta-Trinity National Forest7,232
Mt. Shasta AShasta-Trinity National Forest676
Mt. Shasta BShasta-Trinity National Forest2,809
Mt. Shasta CShasta-Trinity National Forest292
MuseKlamath National Forest238
North Fork SmithSix Rivers National Forest37,898
Orleans Mtn.Klamath National Forest49,090
Orleans Mtn.Shasta-Trinity National Forest57
Orleans Mtn. BSix Rivers National Forest17,183
PacksaddleSix Rivers National Forest3,862
PortugueseKlamath National Forest18,915
RussianKlamath National Forest21,771
ShacklefordKlamath National Forest1,679
Ship MountainSix Rivers National Forest11,936
SiskiyouKlamath National Forest54,039
Siskiyou ASix Rivers National Forest1,017
Siskiyou BSix Rivers National Forest18,871
Slate CreekShasta-Trinity National Forest6,636
SnoozerKlamath National Forest23,414
South KalmiopsisSix Rivers National Forest321
Tom MartinKlamath National Forest9,031
Ukonom CreekKlamath National Forest4,621
West GirardShasta-Trinity National Forest37,516
Oregon (29)
AreaForestAcres
AspenWinema National Forest1,107
Bitter LickUmpqua National Forest179
Brown Mt.Winema National Forest3,117
Bulldog RockWillamette National Forest559
Bulldog RockUmpqua National Forest6,056
Calf - Copeland CreekUmpqua National Forest15,696
Canton CreekUmpqua National Forest6,721
Castle Rock AppendageUmpqua National Forest4,649
CloverWinema National Forest365
Cougar BluffUmpqua National Forest5,574
DoneganUmpqua National Forest5,914
FairviewUmpqua National Forest7,417
Fish Creek AppendageUmpqua National Forest1,377
Jackson Creek AppendageUmpqua National Forest4,673
LastUmpqua National Forest7,666
Limpy RockUmpqua National Forest6,782
Lonesome Meadow AppendageUmpqua National Forest930
Medicine Creek AppendageUmpqua National Forest745
Mt. BaileyUmpqua National Forest18,401
North KalmiopsisSiskiyou National Forests91,560
Rolling Grounds AppendageUmpqua National Forest1,987
Shasta CostaSiskiyou National Forests14,420
SherwoodUmpqua National Forest2,449
Skimmerhorn AppendageUmpqua National Forest1,820
Sky Lakes AWinema National Forest3,940
South KalmiopsisSiskiyou National Forests104,477
Thirsty Creek AppendageUmpqua National Forest2,255
W. BoundaryWinema National Forest2,345
Williams CreekUmpqua National Forest5,844
South Dakota (1)
AreaForestAcres
Indian CreekBuffalo Gap National Grassland24,666
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