Brief Summary

    Bombus affinis: Brief Summary
    provided by wikipedia

    Bombus affinis, commonly known as the rusty patched bumble bee, is a species of bumblebee endemic to North America. Its historical range in North America has been throughout the east and upper Midwest of the United States, north to Ontario, Canada, where it is considered a "species at risk", east to Quebec, south to Georgia, and west to the Dakotas. Its numbers have declined in 87% of its historical habitat range. On January 10, 2017, the United States Fish and Wildlife Service placed B. affinis on the list of endangered species, making the rusty patched bumblebee the first bee to be added to the list in the continental United States (seven species of yellow-faced bees native to the Hawaiian islands were added in 2016).

    Members of B. affinis are relatively large in size, and like other species of bumblebees, are known to be eusocial organisms. Most nests constructed by B. affinis are built underground, and are commonly found in old rodent burrows. Nests created in captivity can house up to 2,100 members, but they are typically much smaller in the wild. This species consumes nectar and pollen from a variety of plants, including Abelia grandiflora, Asclepias syriaca, and Linaria spp. The colony odor is very similar to that of Bombus terricola, which makes it difficult for predators and parasites to differentiate between the two different species.

    Brief Summary
    provided by EOL staff

    The Rusty-patched Bumblebee (Bombus affinis) was at one time among the more common and widespread bumblebees in eastern North America. However, this is no longer the case. The first decade of the 21st century saw growing concern about declining pollinator populations in general in several regions of the world, with particular attention focused on bees, and much of the available data on declining bee populations has focused on bumblebees. Although populations of some bumblebee species appear to be robust, many others have apparently gone extinct in recent years or suffered dramatic declines. Bombus affinis is one of several North American bumblebee species that have experienced clear declines. Colla and Packer (2008) documented an impoverishment of the bumblebee community in general in southern Ontario (Canada) between the early 1970s and the first decade of the 21st century and found that B. affinis, in particular, declined dramatically in abundance not only in southern Ontario but throughout its native range. There is evidence of declines in three other North American bumblebees as well (all four belong to the subgenus Bombus): B. franklini and B. occidentalis in the west and B. terricola in the east. Bombus franklini, which had a historically small geographic distribution, is thought to be at the brink of extinction (or possibly extinct). Bombus affinis, B. terricola, and B. occidentalis have much larger historical ranges, but have disappeared from numerous sites where they were previously common. (Colla and Packer 2008 and references therein)

    The Xerces Society, an organization dedicated to invertebrate conservation, is an excellent resource for more information about Bombus affinis and about broader bumblebee conservation issues.

    Brief Summary
    provided by EOL authors
    The rusty patched bumble bee (Bombus affinis) is named after the small rust-colored patch visible on worker bees' abdomens. Worker bees also have yellow on the first and rear half of the second abdominal segment. The remaining abdominal segments are black. Queens and males resemble workers except that they lack the rust-colored patch. Queens are larger in size than workers and have a small central bare patch on the thorax. This bee was historically found throughout the eastern and upper midwestern United States. However, surveys between 2003 and the present have found only a small number of this species in Illinois and Wisconsin.

Comprehensive Description

    Bombus affinis
    provided by wikipedia

    Bombus affinis, commonly known as the rusty patched bumble bee, is a species of bumblebee endemic to North America.[3] Its historical range in North America has been throughout the east and upper Midwest of the United States,[4] north to Ontario, Canada, where it is considered a "species at risk",[5] east to Quebec, south to Georgia, and west to the Dakotas.[5] Its numbers have declined in 87% of its historical habitat range.[4] On January 10, 2017, the United States Fish and Wildlife Service placed B. affinis on the list of endangered species, making the rusty patched bumblebee the first bee to be added to the list in the continental United States[6] (seven species of yellow-faced bees native to the Hawaiian islands were added in 2016).

    Members of B. affinis are relatively large in size, and like other species of bumblebees, are known to be eusocial organisms.[3] Most nests constructed by B. affinis are built underground, and are commonly found in old rodent burrows.[3] Nests created in captivity can house up to 2,100 members, but they are typically much smaller in the wild.[3] This species consumes nectar and pollen from a variety of plants, including Abelia grandiflora, Asclepias syriaca, and Linaria spp.[3] The colony odor is very similar to that of Bombus terricola, which makes it difficult for predators and parasites to differentiate between the two different species.[7]

    Taxonomy and phylogeny

    B. affinis is a member of the subfamily Apinae,[3] and is most closely related phylogenetically to B. franklini, which is another species of bumble bee endemic to North America.[8] B. affinis is in the company of nearly 250 other species of bumblebee worldwide in the genus Bombus,[3] although only 50 are native to parts of the US and Canada.[3] Unlike many other members of the genus Bombus, B. affinis workers and queens are characterized by different color patterns, which allow observers to tell them apart.[9]

    Description and identification


    Large differences are seen in morphology between both queens and workers, and males and females.[9] Queens are about 20–22 mm (0.79–0.87 in) in length and 9–11 mm (0.35–0.43 in) in width, which is larger than workers that are typically about 10–16 mm (0.39–0.63 in) in length and 6–9 mm (0.24–0.35 in) in width.[9] Both queens and workers have black hair that covers their heads, much of their legs, and the bottom of their abdomens.[9] They also both have completely yellow hair on the majority of their abdomens, except for a small section near the area closest to the rear end of the bee.[9] Workers have a slight mixing of yellow and black hairs near the base of the wings, which forms a discernible "V" shape, as well as a rust-colored patch of hair on the middle portion of the abdomen.[9] Thus, while workers and queens share similarities in certain aspects of coloration, also differences occur in body size and the presence or absence of rust-colored patches of hair.[9] Regardless of the caste within the colony, all members of B. affinis have significantly shorter tongues than any other species of bumblebee.[9] Because of its body size and furry appearance, however, this bee is often confused with other species of bumblebee, such as B. citrinus, B. griseocollis, B. perplexus, and B. vagans.

    Furthermore, male and female workers of B. affinis also differ in terms of their appearance and body size. Male workers are typically slightly larger than females (13–17.5 mm (0.51–0.69 in) in length), and have a few off-white/pale hairs present on tops of their heads.[9] They also have black hair which sometimes streaks across the tops of their abdomens (which are typically yellow).[9] Finally, males can even have pale yellow hair on their abdomens, as opposed to the normal shade of yellow observed in females and queens.[9]


    B. affinis bees are known to build their nests underground in locations such as ditches on the side of the road, wetlands, and fields.[8] However, nests are sometimes constructed above ground in chunks of grass and soil, which can be limited by the availability of open grasslands.[9] A B. affinis nest was once found inside an armchair that was abandoned outside.[3] When nests are constructed underground, though, they are typically located 16–18 in (410–460 mm) below the surface, and are composed of soft soil.[9]

    Distribution and habitat

    B. affinis requires three different types of habitats (each for foraging, nesting, and hibernating)[8] which are geographically close to one another, making this species particularly vulnerable to extinction.[8] It requires a temperate climate, and can even withstand cold temperatures that most species of bumblebees cannot.[3] In addition, B. affinis has been found at elevations as high as 1600 m.[3] B. affinis is known to visit a number of sites for foraging, including sand dunes, farmland, marshes, and wooded areas.[3] Members actively forage between April and October, thus requiring flowers to bloom for a long period of time.[3] B. affinis nests are strikingly similar to other species of bees, which makes them difficult to locate.[3] However, queen and workers work together to make individual cells and honey pots out of wax stores.[10] In terms of their hibernating habitat, little information is known.[3] B. affinis queens overwinter, but they most likely will live underground or burrow into rotting logs during the winter to survive.[3] While B. affinis' habitat used to be highly prevalent, a large decline has occurred in recent years, possibly due to increased land development and agricultural use.[8]

    Until the 1980s, it was one of the most common species of bumblebee in southern Ontario. Since then, the species has had a drastic decline in number and is now difficult to find in its normal range.[5] The only locality within Ontario where the rusty patched bumblebee has been seen in the last five years is Pinery Provincial Park (Lambton County), despite widespread surveys in Ontario.[5] The Ontario Ministry of Natural Resources has begun a recovery project aimed at protecting the species and critical habitats centered in Pinery Provincial Park.[5] These threats have been proposed as the cause of population decline: pathogen spillover from other species, pesticide use, and habitat fragmentation and loss.[5] Surveys from 2001–2008 have located B. affinis populations only in Illinois, Iowa, Maryland, and southern Ontario.[4]

    Colony cycle

    Colony initiation and growth

    New colonies are started by B. affinis in the spring and decline in the fall.[8] Members of this species actually emerge before most other species of Bombus, and continue foraging after other species have begun hibernating.[8] Solitary queens are the first to emerge and begin searching for a colony, while also collecting nectar and pollen to feed her future brood.[9] The queen uses sperm she has saved from her mating activities of the previous fall to fertilize her eggs.[9] Eggs hatch about four days after fertilization, but take up to 5 weeks to become completely developed adults depending on temperature and food availability.[3] In the first few weeks after laying her brood, the queen is solely responsible for feeding her young.[9] However, shortly afterwards, her female worker offspring begin collecting food for the colony in preparation for more offspring.[9] Once the workers are able to become the primary caretakers of the nest, the queen can focus on laying more eggs.[9] At this point (which is about halfway through the summer), the number of workers reaches an optimal number and the queen begins producing males and potential new queens.[9] Colony sizes can range from 50 to 400 individuals, although colonies raised in captivity are known to get much larger, having as many members as 2100.[9]

    Colony decline

    During this half-way point in the summer, any members with reproductive potential leave the nest and begin mating.[3] The number of potential queens that can be produced is heavily reliant on the amount of nectar and pollen that can gathered during this time.[9] Thus, a shortage of food may result in lesser queen production, and vice versa.[9] Because solitary queens are the only members of the B. affinis that can initiate new colonies, the success of future colonies is dependent on queen production.[9] Furthermore, after mating, new queens rest and enter into diapause, or hibernation for the winter.[9] Male members and workers decline as the weather gets colder, and eventually die when winter comes.[3] Thus, colonies live for about 4–5 months depending on the environmental conditions.[3] Queens commonly die at different times throughout colony production, which can often lead to orphaned colonies.[11] Queens typically live for about 77 days on average.[11]

    Reproductive suppression

    Similar to other social insects, egg laying by B. affinis workers is suppressed by the presence of a dominant queen that is capable of reproducing.[10] The queen's position as a dominant member or leader of the colony is made known through both pheromones and behavioral patterns.[10] However, strictly the presence of specific pheromones suppresses gonadotropic hormones in B. affinis workers, leading to suppressed reproductive potential.[10] Variability exists in dominance signals both between certain species, and also between subspecies or subgenera.[10] For example, in B. terrestris colonies, presence or absence of abdominal glands rather than pheromones dictates the dominance of the queen.[10] In the absence of a fecund queen, aggression and violence between workers increases quickly.[10] In addition, ovarian weight is significantly lower in colonies where the queen is present than when she is removed.[10]

    Bombus bohemicus (an obligate brood parasite of B. affinis) was once thought to play a role in suppressing ovarian development in B. affinis, but this is not the case[10]. Members of the subgenus Psithyrus often maul other members of the host colony, which indirectly decreases the number of eggs laid in the host colony.[10] B. bohemicus does not demonstrate this behavior, and actually has worse chances of survival in nests where a dominant queen is not present, due to increased aggression by B. affinis members.[10] However, while ovarian development is not impacted by the presence of B. bohemicus, overall reproductive success is decreased due to consumption of the host eggs and larval ejection.[10]

    Kin selection

    Genetic relatedness

    Genetic relatedness within the B. affinis species varies depending on the relationship.[11] Because members are haplodiploid making males haploid and females diploid, so genetic relatedness is asymmetrical, causing workers to be more closely related to their sisters than their brothers.[11] B. affinis workers share a correlation coefficient (or variable indicating the strength of the relatedness/ degree of relatedness) of r = 0.75 with full sisters but only r = 0.25 for full brothers.[12] In addition, workers are also much more closely related to their sons than their own brothers, and even more so than their nephews.[11] The r value is likely greater than 0.5 for sons.[12] While it is advantageous for ratio of males to queens to be 1:1 normally, this asymmetry in genetic relatedness results in much conflict between the queen and the workers.[11] Thus, all members which are workers should demonstrate favor for a predominantly female population (if the queen is the major egg layer in the colony).[11]

    Worker/queen conflict

    Differences in genetic relatedness can result in conflict between the B. affinis queen and workers.[11] This conflict can manifest itself either through a skewed sex ratio with the absence of any physical aggression or through direct contact in which one member will act violently towards another member to inhibit reproductive success.[11] Should aggression manifest itself as skewed sex ratios, the ratio of male to female offspring varies depending on the contribution from queens and workers.[11] For example, if there is no worker contribution, the ratio will be 1:3 (males to females), however, if contribution is solely from workers, then the ratio be far closer to 1:1.[11] However, should the aggression manifest itself as violent behaviors, they will often be directed toward a member's brood, through actions such as larval ejection.[11] This larval ejection is often associated with the degradation of group cohesion, and typically occurs at a late stage in colony development.[11] It can also be the result of workers attempt to lay their own eggs, independently of the queen.[11]

    Interaction with other species


    B. affinis is parasitized most extensively by a separate species of bee, Bombus bohemicus, which is an obligate brood parasite.[7] B. bohemicus ends hibernation shortly after B. affinis, and searches for their established nests, but the exact mechanism is unknown.[7] Females of B. bohemicus are thought to be able to locate the host nests by identifying the odor from a distance—without ever having physical contact with the nest or regions that were used by workers.[7] By flying low to the ground and searching carefully (even by looking near leaves and debris), B. bohemicus may first locate the entrance of a B. affinis nest, and then verify its findings by odor identification.[7] After invading the nest, however, the B. bohemicus lives alongside the queen and the workers, and also attempts to rear its own brood (which must be raised with host workers' help).[11] Because larger nests tend to have more workers defending the nest, B. bohemicus often invades smaller nests, which forces it to occupy smaller nests for a longer time.[11] B. bohemicus is uniquely found in the nests of B. affinis and B. terricola, where it is usually tolerated if unnoticed. However, B. affinis has been known to exhibit oophagy (or consumption of nonhost eggs), larval ejection, and ejection of the parasite in response to parasite presence.[11] Should B. bohemicus make a mistake in invading the nests of other species, they will be attacked by the queen, whose violent actions often end in their death.[7]


    B. affinis consumes the nectar and pollen of a variety of nototrobic plant species, including Lobelia siphilitica, Linaria vulgaris, and Antirrhinum majus.[13] Dicentra cucullaria, a flowering plant, is particularly dependent on members of the B. affinis for sexual reproduction.[14] In fact, the flower structure and mechanism by which it is pollinated indicate that it is adapted for foragers such as B. affinis, which can separate the outer and inner petals of the flower.[14] Members then use their front legs to expose the stigma, stamen, and anthers.[14] Shortly afterwards, they sweep pollen in a forward stroke by using their middle legs, before leaving the flower to return to the colony with the pollen.[13] In this way, D. cucullaria is pollinated as the bees move from plant to plant, and B. affinis meets its dietary needs.[13] This pollen foraging behavior is strikingly similar to bees of the genus Apis.[14] Species of the Apis are lighter in weight, though, making it slightly more difficult to gain access.[13]


    B. affinis is susceptible to a certain species of protozoa, known as Apicystis bombi.[15] This pathogen affects about 3% of all B. affinis, and is particularly prevalent in Ontario.[15] A. bombi first infects the gut of its host, then spreads this infection to the rest of the body.[16] While its transmission is not well understood, A. bombi causes multiple negative effects, including increased death of worker bees, and the prevention of formation of new colonies.[16] It also limits ovarian development of queens, and reduces their lifespans.[16] This disease likely was introduced to North America by commercial B. terrestris in the early in early 2005 or 2006 when members invaded northern Patagonia, Argentina, from Europe.[15] A. bombi rarely affects bees occupying Europe (only about 6-8% show signs of infection); however, for European bees living in Patagonia, incidence of infection is closer to about 50% in certain species.[16] Because of this, conservation experts are concerned that A. bombi may be detrimental to several bumblebee species, including B. affinis.[16]

    Importance in agriculture

    B. affinis is important to the agricultural industry.[9] This species pollinates up to 65 different genera[17] of plants, and is the primary pollinator of key food crops, such as cranberries, plums, apples, onions, and alfalfa.[3] These crops are important for day-to-day consumption by humans, but are also vital to sustaining birds and mammals that feed on their fruit.[3] Plants pollinated by B. affinis (such as Aralia and Spiraea) are used medicinally by aboriginal peoples of Canada known as the First Nations.[3] Thus, the recent decline of B. affinis could have far-reaching effects on ecosystems, economic stability, and cultural traditions.[3]

    In 2008, three recent events were reported to have led to the decline of B. affinis' agricultural role: pathogen spillover, pesticide use, and habitat loss.[8] Many bumblebees used in commercial businesses harbor harmful parasites that can impact nearby wild populations of B. affinis.[8] This often has lethal effects, and has led to the decline of B. terricola and B. impatiens, as well.[8] Aside from pathogen spillover, however, novel pesticides also affect populations of B. affinis.[8] Neonicotinoids are pesticides that are toxic to bees in particular, but they are commonly used for pest control on crops and turf.[8] Because B. affinis nests are built underground, they are uniquely susceptible to this pesticide's use on turf.[9] Lastly, increases in urbanization and industrialization have meant the loss of native habitats.[8] While other species such as B. bimaculatus, the two-spotted bumble bee, have adapted well to urban environments, B. affinis has not.[8] Whether the reduction of native food plants in particular has affected B. affinis is not known.[8]

    See also


    1. ^ Bombus affinis, IUCN
    2. ^ "Bombus affinis". Biolib.cz. Retrieved 18 Sep 2013..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"""""'"'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
    3. ^ a b c d e f g h i j k l m n o p q r s t u v w x Canada, Government of Canada, Environment. "COSEWIC Assessment and Status Report on the Rusty–patched Bumble Bee Bombus affinis in Canada – 2010 - Species at Risk Public Registry". registrelep-sararegistry.gc.ca. Retrieved 2015-10-11.
    4. ^ a b c Rusty-patched Bumblebee, Xerces Society
    5. ^ a b c d e f "Rusty-patched Bumblebee (Bombus affinis) in Ontario Ontario Recovery Strategy Series" (PDF). Recovery strategy prepared under the Endangered Species Act, 2007. Ministry of Natural Resources. 2011. Retrieved 8 August 2012.
    6. ^ Abel, David (2017-01-10). "The plight of the bumblebee". Boston Globe. Retrieved 2017-01-11.
    7. ^ a b c d e f "Recognition of Host Nest Odour by the Bumblebee Social Parasite Psithyrus ashtoni (Hymenoptera: Apidae) on JSTOR". JSTOR 25009392. Missing or empty |url= (help)
    8. ^ a b c d e f g h i j k l m n o Colla, Sheila R.; Packer, Laurence (2008-02-08). "Evidence for decline in eastern North American bumblebees (Hymenoptera: Apidae), with special focus on Bombus affinis Cresson". Biodiversity and Conservation. 17 (6): 1379–1391. doi:10.1007/s10531-008-9340-5. ISSN 0960-3115.
    9. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z Evans, Elaine. "Status Review of Three Formerly Common Species of Bumble Bee in the Subgenus Bombus" (PDF). The Xerces Society for Invertebrate Conservation. The Xerces Society for Invertebrate Conservation. Retrieved 10 October 2015.
    10. ^ a b c d e f g h i j k l "Inability of the Social Parasite Psithyrus ashtoni to Suppress Ovarian Development in Workers of Bombus affinis (Hymenoptera: Apidae) on JSTOR". JSTOR 25084374. Missing or empty |url= (help)
    11. ^ a b c d e f g h i j k l m n o p q "Queen-worker conflict and social parasitism in bumble bees (Hymenoptera: Apidae)". Animal Behaviour. 35: 1026–1036. doi:10.1016/S0003-3472(87)80159-8. Retrieved 2015-10-13.
    12. ^ a b Gadagkar, Raghavendra (1991-04-01). "On testing the role of genetic asymmetries created by haplodiploidy in the evolution of eusociality in the Hymenoptera". Journal of Genetics. 70 (1): 1–31. doi:10.1007/BF02923575. ISSN 0022-1333.
    13. ^ a b c d "Pollen-Foraging Behavior of Bombus in Relation to Pollination of Nototribic Flowers on JSTOR". JSTOR 2440764. Missing or empty |url= (help)
    14. ^ a b c d Macior, Lazarus Walter (1970-01-01). "The Pollination Ecology of Dicentra cucullaria". American Journal of Botany. 57 (1): 6–11. doi:10.2307/2440374. JSTOR 2440374.
    15. ^ a b c Jepsen, Sarina, et al. "Petition to List the Rusty Patched Bumble Bee Bombis Affinis (Cresson, 1863) as an Endangered Species Under the U.S. Endangered Species Act." The Xerces Society for Invertebrate Conservation, 31 Jan 2013. PDF File. 12 Oct 2015.http://www.xerces.org/wp-content/uploads/2013/01/Bombus-affinis-petition.pdf[permanent dead link]
    16. ^ a b c d e "Newsletter of the BumbleBee Specialist Group" (PDF). Bumblebee Conservator. 2014.
    17. ^ egistrelep-sararegistry.gc.ca/default.asp?lang=En&n=0F864E45-1


    provided by EOL staff

    The historical range of Bombus affinis extends from southern Ontario and southwestern Quebec (but apparently not New Brunswick, contrary to apparently erroneous literature references) in Canada south to Georgia and west to the Dakotas in the United States, with occurrences in the southern portion of the range limited mainly to higher elevations (Thorp and Shepherd 2005; Colla 2010).

    provided by Catalog of Hymenoptera in America North of Mexico
    Que. and Ont. south to Ga., west to S. Dak., N. Dak., Iowa, and Ala. (N.B., Ont., Que., Ala., Conn., Del., Ga., Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., N.H., N.J., N.Y., N.C., N. Dak., Ohio, Pa., R.I., S.C., S. Dak., Tenn., Vt., Va., W. Va., and Wis.), but see comment below.


    provided by EOL staff

    Bombus affinis queens and workers differ slightly in coloration (an uncommon feature in bumble bees). Other than size, the primary difference between queens and workers is the presence of a medial rusty patch on the second abdominal segment of the worker. The hairs of workers are entirely black on the head, the bottom of the thorax, and in large part on the legs. The rest of the thorax has mostly yellow hair, with a black area in the middle of the thorax. Hairs are entirely yellow on the first two abdominal segments and black on the rest of the abdomen. On workers, there is more black intermixed with yellow near the base of the wings, forming something of a band between the wings, and black hairs extend posteriorly in a narrow "V" that partially bisects the yellow on the scutellum. The second abdominal segment has a rusty reddish patch centrally, with yellow hairs around the edges of the segment. Bombus affinis males have hairs largely black on the head, but with a few pale hairs intermixed near the top of the head. Black hairs sometimes form an obscure band across the middle of the thorax, but the hair on the thorax is otherwise largely pale yellowish. The first two abdominal segments have pale yellow hair. The hair on the rest of the abdominal segments is black. (Evans et al. 2008)


    provided by EOL staff

    Bombus affinis has been collected in a wide variety of habitats including mixed farmland, sand dunes, marshes, and both urban and wooded areas (Colla 2010).


    provided by EOL staff

    Macfarlane (1974, cited in Colla and Packer 2008) observed B. affinis visiting at least 65 plant genera. These bees have been observed biting holes (i.e. nectar-robbing) in flowers with long corolla tubes such as Jewelweed (Impatiens capensis), Yellow Toadflax (Linaria vulgaris) (R. Gegear pers. comm., cited in Colla and Packer 2008), and Cow Vetch (Vicia cracca) (Harder 1983, cited in Colla and Packer 2008).

    Bombus affinis is one of two host species for the socially parasitic Bombus (Psithyrus) ashtoni (the other host being the also declining B. terricola) (Fisher 1983). In 2010, Colla reported that B. ashtoni had not been observed in a decade. Bombus species in the subgenus Psithyrus lack pollen-collecting corbiculae and rely on the host workers for the rearing of reproductives. Sladen (1912, cited in Fisher 1983a) reported that the host queen was always killed or displaced by the invading Psithyrus, while Plath (1934, cited in Fisher 1983a) found that in the case of the two North American Psithyrus species he studied (B. ashtoni and B. citrinus) the queen was seldom killed. Subsequent investigations showed that B. ashtoni never kills queens of either of its host species, B. affinis and B. terricola (Fisher 1983a). Fisher found that B. ashtoni is incapable itself of suppressing ovarian development in queenless workers of B. affinis. An alternative strategy to physiological suppression of oogenesis is behavioral domination. Fisher reported that B. ashtoni females were often seen mauling workers, i.e., grasping and pulling them underneath the body as if to sting, but not actually doing so. This behavior only occurred in colonies which had no queen or had a queen that had lost her dominance (ovarian development of workers is normally supressed by the queen). Physical dominance by B. ashtoni females would not prevent oogenesis, but could eliminate or minimize egg laying by fecund workers. Fisher presented data suggesting that females of B. ashtoni benefit by the supression of host worker reproduction by the host queen. At the same time, B. ashtoni females prevent Bombus affinis males and queens from developing by selectively eating eggs and ejecting larvae. The non-aggressive invasion strategy used by B. ashtoni is quite distinct from that of other Psithyrus species, such as B. citrinus, which according to Fisher always kills or displaces its B. impatiens host queen. These other species presumably possess themselves the physiological or behavioral means of eliminating or reducing the frequency of egg laying by host workers in the nests they invade and thus do not need to rely on the host queen to control the workers. (Fisher 1983a) Fisher (1983b) investigated host nest finding by B. ashtoni. These bees search for nests within one to two weeks of host queen emergence at a time prior to emergence of the first worker brood and therefore cannot use odor trails of workers to recognize nests. In laboratory experiments, Fisher showed that B. ashtoni females can recognize host nest odor without actual contact with the nest or with worker-laid trails, successfully distinguishing nests of B. affinis and B. terricola from those of B. bimaculatus and from controls consisting only nest material.

    Martin et al. (2010) investigated the cuticular hydrocarbon cues of 14 European Bombus species, including 5 socially parasitic species ("cuckoo bees" in the subgenus Psithyrus) (B. affinis, B. ashtoni, or any other North American species, were not among the species studied, but the general conclusions of the analysis by Martin et al. likely apply more broadly). They found that found that bumblebees possess species-specific alkene positional isomer profiles that are stable over large geographic regions and are mimicked by three host-specific Psithyrus parasites. In three host-cuckoo associations where mimicry is poor, possibly as a result of recent host shifts, these cuckoos produce dodecyl acetate a known chemical repellent that allows the cuckoos to invade their host colonies. Thus, various Psithyrus species may use both mimicry and repellents to invade host colonies.

    Microscopic endoparasites recorded infecting B. affinis include Sphaeruluria bombi (a nematode infecting 10% of overwintered queens) and the apicomplexan protozoan Apicystis bombi (Neogregarinida: Ophrocystidae) (Macfarlane et al. 1995, cited in Colla 2010). Other parasites that are known to infect sympatric Bombus species are Nosema bombi (Microsporidia: Nosematidae) and the trypanosome protozoan Crithidia bombi (Kinetoplastea: Trypanosomatidae), both of which may be acquired at flowers via fecal transmission (Colla et al. 2006). Nosema bombi has recently been found infecting B. affinis (Cameron et al. 2011), but infection of B. affinis by C. bombi has apparently not yet been documented (possibly because of the relative recency of the presumed introduction of this parasite from Europe in combinatuon with the rarity of B. affinis in recent years) (Colla 2010). Several species of parasitoid conopid flies (Diptera: Conopidae) attack foraging bumblebees on the wing and lay their eggs inside the bee’s abdomen. (Gillespie 2010 and references therein)

    Conopids and C. bombi can affect colony reproduction and worker foraging behavior. Nosema bombi may reduce colony fitness and worker survival. These parasites could affect local abundance of bumblebee populations and C. bombi and N. bombi have been tentatively implicated in the overall decline of bumblebees. In a study in Massachusetts, Gillespie (2010) found a high level of parasitism of bumblebees by C. bombi, N. bombi, and conopid flies (although no B. affinis were encountered in this study). (Gillespie 2010 and references therein)

    Bombus affinis has been shown to be an excellent pollinator of cranberry and also to pollinate other important crops such as plum, apple, alfalfa, and onion for seed production. Evans et al. provide a long list of wild plants known to be visited by B. affinis. (Evans et al. 2008 and references therein).

General Ecology

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    The flight season of Bombus affinis is longer than that of most other North American bumblebees and it visits numerous plant genera in diverse habitats (Colla 2010).

    Bombus affinis have relatively short tongues. On average, the tongues of workers are around 5 to 7 mm in length (some other bumblebee species have tongues as long as 10 mm). Their short tongues make them unable to access the nectar in flowers with deep tubes, although they sometimes use their mandibles to chew holes in the bottom of these flowers to access the nectar from the outside of the flower, thus cheating the flower of pollination. (Evans et al. 2008 and references therein)

    General Ecology
    provided by Catalog of Hymenoptera in America North of Mexico
    Frequently usurps colonies of Bombus terricola Kirby.


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    Bombus affinis typically nests underground in abandoned rodent burrows located from six to eighteen inches below the surface. Occasionally nests are constructed on the surface in areas such as clumps of grass on the ground. Thus, nesting sites may be limited by the abundance of rodents and the presence of undisturbed grassland. (Evans et al. 2008 and references therein).

    Brood cells and honey pots are made of wax produced by the queen and workers. Like other bumblebees, B. affinis have an annual life cycle (i.e., 1 year = 1 generation). Mated queens emerge from diapause in the spring to begin feeding and searching for potential nest sites to initiate new colonies. The queen collects nectar and pollen from flowers to support the production of her eggs (which are fertilized by sperm she has stored since mating the previous fall) and produces a brood of workers. In the early stages of colony development, the queen is responsible for all food collection and care of the young. As the colony grows, workers take over the duties of food collection, colony defense, and care of the young. The queen then remains within the nest and spends most of her time laying eggs. As the summer progresses, the colony reaches maximum worker production and begins producing males and potential queens (queen production is dependent on access to sufficient quantities of pollen). These reproductive individuals leave the colony and mate. After mating, young queens enter diapause and overwinter. The males and workers decline as fall approaches until they die in the winter. (Evans et al. 2008; Colla 2010).

    The largest B. affinis colony on record produced 2,100 individuals in captivity (MacFarlane 1974, cited in Colla 2010), but in the wild colonies are much smaller (Colla 2010). More typically, B. affinis colonies consist of a queen and between 50 and 400 workers at their peak (Evans et al. 2008).

    Bombus affinis is a "pollen-storer", meaning the larvae live in cells and are fed individually by adults opening the brood clump as the larvae develop. Pollen-storing adults emerge relatively equal in size compared to "pocket-making" bumble bee species, which tend to produce workers that vary greatly in size due to unequal food distribution within the brood clumps during development. (Colla 2010)


    Systematics and Taxonomy
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    Bombus affinis was first described by Cresson in 1863. Although the taxonomy of some bumble bee species is controversial, the status of B. affinis as a distinct, valid species is not (Cameron et al. 2007).


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    Because of the particular haplodiploid mode of sex determination characteristic of bees, which normally yields diploid females and haploid males but results in the production of non-viable diploid males when allelic diversity is low (and hence homozygosity is high), effective population size relative to census size is much reduced and bee populations in general may therefore be especially vulnerable to extinction as population size shrinks (Zayed and Packer 2005).

Conservation Status

    IUCN Red List: Bombus affinis (Rusty Patched Bumble Bee)
    provided by EOL authors

    IUCN Red List species profile (current status: Critically Endangered)

    USFWS Endangered Species: Rusty Patched Bumble Bee (Bombus affinis)
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    "Just 20 years ago, the rusty patched bumble bee was a common sight, so ordinary that it went almost unnoticed as it moved from flower to flower, collecting nectar and pollen. But it's now balancing precariously on the brink of extinction and has become the first-ever bumble bee in the United States -- and the first bee of any kind in the contiguous 48 states -- to be declared endangered."


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    In the 1970s, Bombus affinis was among the more common and widespread bumblebee species in eastern North America. Dramatic declines were noted by the mid-1990s in both Canada and the United States. In Canada, extensive targeted searches from 2005 to 2009 detected just three individuals (one in 2005 and two in 2009). Similar population crashes have been observed in the U.S. (Colla 2010 and references therein)

    According to an analysis by Cameron et al. (2011), the relative abundances of four North American bumblebee species have declined by up to 96% and their geographic ranges have contracted by an estimated 23% to 87%, some within a span of two decades. In the recent large-scale bumblebee survey carried out by Cameron et al., which included the capture and identification of nearly 17,000 individuals (most of which were released), only 22 B. affinis individuals were found, and although this species was once found throughout the eastern United States and northern Midwest, individuals were detected at just three locations in Illinois and one in Indiana (yielding an estimated range reduction of 87%).

    Grixti et al. (2009) found that bumblebee species richness in Illinois (U.S.A.) declined substantially during the middle of the century (1940 to 1960). Four species were locally extirpated: B. borealis, B., B. terricola and B. variabilis. The ranges of B. affinis, B. fraternus, B.pensylvanicus and B. vagans have also decreased dramatically in Illinois. The major decline in the Illinois bumblebee fauna coincided with large-scale agricultural intensification in Illinois, suggesting one likely factor driving bumblebee declines.


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    The reasons for the sudden decline of Bombus affinis, a previously common species throughout its large range, are unknown. It has been suggested that, along with other vulnerable North American species in the subgenus Bombus (B. occidentalis, B. terricola, and the possibly extinct B. franklini), the species has suffered from introduced diseases transmitted from managed bumblebee colonies used for greenhouse pollination. In addition, habitat loss and the widespread use of certain pesticides likely represent significant threats. (Evans et al. 2008; Colla 2010)

    A variety of circumstantial evidence supports the hypothesis that at least some recent bumblebee declines in North America have been driven or exacerbated by the spread of Nosema bombi, an obligate intracellular microsporidian fungal parasite found commonly in bumblebees throughout Europe, via commercial bumblebee rearing facilities that introduced this pathogen from Europe. Pathogenic effects of N. bombi may vary depending on the host species and reproductive caste, but they may include reductions in both colony growth and individual life span and fitness. Further research will be necessary to clarify the role of pathogens in bumblebee declines. (Cameron et al. 2011 and references therein) Based on a combination of modeling, laboratory experiments, and literature review, Otterstatter and Thomson (2008) found strong support for the hypothesis that spillover of Crithidia bombi (a destructive internal trypansomatid protozoan parasite) from bumblebees reared commercially to pollinate greenhouse crops has contributed to the ongoing decline of wild Bombus in North America. Wild bumblebees may also be negatively impacted by the spread of the bumble bee tracheal mite Locustacarus buchneri to wild populations from commercially reared colonies (Evans et al. 2005 and references therein).