rusty-patched bumble bee

(Bombus affinis)

Conservation Status
rusty-patched bumble bee
Photo by Babette Kis
  IUCN Red List

CR - Critically Endangered


NNR - Unranked

SNR - Unranked




not listed

Species in Greatest Conservation Need


Rusty-patched bumble bee is a relatively large colonial bumble bee. It was historically common throughout most of its range, which extended from Maine to Georgia, west to Minnesota, with a few individuals found in North Dakota. Since the 1990s populations have declined severely in 87% of its historical range. It currently occurs in Minnesota, Iowa, Wisconsin, Illinois, and Indiana, and there are a few widely scattered recent records from Ontario, Quebec, Ohio, New York, Massachusetts, Virginia, and West Virginia.

The female (worker) bee is 716 to (11 to 16 mm) long. The width of the abdomen is 316 to 516 (5 to 8 mm).

The hairs on the head are entirely black, including a dense band of hairs on top of the head (vertex) at the rear. The antennae have 12 segments consisting of one basal segment (scape), one small connecting segment (pedicel), and ten more segments (flagellomeres). The scape is long, slightly more than half as long as all of the flagellomeres together. The first flagellomere is slightly longer than the third, and the third is somewhat longer than the second. The tongue is short, shorter than any other bumble bee species.

The upper side of the thorax is densely covered with long, mostly yellow hairs. The hairs near the flap-like covering of the wing bases (tegulae) are black intermixed with yellow. Between the wings there is a band of black hairs that extends toward the rear in a V shape.

The abdomen has six segments and is densely covered with relatively long hairs. The hair on the first segment is entirely yellow. On the second segment it is mostly yellow except for a rusty-red patch in the middle. On the remaining segments the hairs are entirely black.

The wings are clear and lightly tinted brown.

The legs are black and are covered with mostly black hairs.

The queen is similar but larger, 1316 to (21 to 22 mm) in length. The pubescence is shorter and less dense. The thorax has a round, bare, black spot in the middle surrounded with intermixed black and yellow hairs. The second abdominal segment is entirely yellow, with no rusty patch.

The male (drone) is somewhat larger, ½ to 1116 (13.0 to 17.5 mm) in length. It is similar to the worker, but the abdomen has 7 segments, and the antennae have 13 segments. The band of hairs on the vertex has a few pale hairs intermixed. The hairs on abdominal segments 1 and 2 are entirely yellow.




Male: ½ to 1116 (13.0 to 17.5 mm)

Worker: 716 to (11 to 16 mm)

Queen: 1316 to (21 to 22 mm)


Similar Species






Mid-May through late October






Life Cycle


Rusty-patched bumble bee usually nests in the ground in an abandoned rodent burrow.


Larva Food




Adult Food




Distribution Map


The map at left includes counties in which

  • rusty-patched bumble bee is believed to occur but for which there are no records (yellow)
  • there are no records after 2005 (light green)
  • there are post 2005 records, including citizen science records (dark green)



4, 24, 27, 29, 30, 82, 83.

Environmental Conservation Online System (ECOS), U.S. Fish and Wildlife Service, Rusty patched bumble bee (Bombus affinis), retrieved 2/2/2023.

Minnesota Bee Atlas, University of Minnesota Extension, © 2023 Regents of the University of Minnesota, Bombus affinis (rusty-patched bumble bee), retrieved 2/2/2023.







Hymenoptera (ants, bees, wasps, and sawflies)  


Apocrita (narrow-waisted wasps, ants, and bees)  


Aculeata (ants, bees, and stinging wasps)  


Apoidea (bees and apoid wasps)  
  Epifamily Anthophila (bees)  


Apidae (honey bees, bumble bees, and allies)  


Apinae (apine bees)  




Bombus (bumble bees)  
  Subgenus Bombus  

Some authors separate bumble bees and orchid bees into the subfamily Bombinae. NCBI follows this classification. Most authors follow Michener (2007) and include those groups in the subfamily Apinae with the honey bees.




Bremus affinis


Common Names


rusty patched bumble bee

rusty-patched bumble bee












A segment of the whip-like third section of an insect antenna (flagellum).



On plants: An erect, leafless stalk growing from the rootstock and supporting a flower or a flower cluster. On insects: The basal segment of the antenna.



A small, hardened, plate, scale, or flap-like structure that overlaps the base of the forewing of insects in the orders Lepidoptera, Hymenoptera, Diptera, and Homoptera. Plural: tegulae.



The upper surface of an insect’s head.





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Babette Kis

    rusty-patched bumble bee      

Bombus affinis rusty patched bumblebee

… rusty patched bumblebee, Bombus affinis, on Eryngium yuccifolium, rattlesnake master.

  rusty-patched bumble bee  
    rusty-patched bumble bee   rusty-patched bumble bee  





Bombus affinis
USGS Bee Inventory and Monitoring Lab
  Bombus affinis  
Bombus affinis
Lisa King
  Bombus affinis  

Rusty-patched Bumble Bee




Visitor Videos

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Other Videos
  Rusty-patched bumble bee, Bombus affinis, queen and male observations at nest site in Red Wing, MN.

Aug 17, 2020

This video highlights queen and male observations at a rusty-patched bumble bee nest at Red Wing, MN. The rusty-patched bumble bee was listed as federally endangered under the Endangered Species Act in 2017 and nest sightings are incredible rare. Entomologist and graduate researcher, Michelle Boone, shares observations made in August 2020. The Cariveau Native Bee Lab of the University of MN Entomology Department conducted nest studies at two known nest locations in the summer of 2020, led by Dr. Elaine Evans.

  Forgotten But Not Gone: The Rusty Patched Bumble Bee | bioGraphic

Mar 8, 2017

Despite swift population declines, this native bee has never received formal protection. Can a listing save it from extinction?

There are 47 varieties of native bumble bee in the United States and Canada, and the International Union for Conservation of Nature (IUCN) estimates that more than a quarter of those species face the threat of extinction. But unlike honeybees—an imported species from Europe whose recent mass deaths have been well publicized and extensively researched—bumble bees receive scant attention. If the federal listing of the rusty patched bumble bee proceeds, however, that may change: It would be the first native bee in the continental United States to be protected under the Endangered Species Act.

Video by Day's Edge Productions. Read the full story here:




Visitor Sightings

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  Babette Kis

Location: southeastern Wisconsin

… rusty patched bumblebee, Bombus affinis, on Eryngium yuccifolium, rattlesnake master.

rusty-patched bumble bee  
  Babette Kis

Location: southeastern Wisconsin

rusty-patched bumble bee  






Created: 2/2/2023

Last Updated:

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