The Patagonian Bumblebee

Bombus dahlbomii

Mackenzie Rupe

Taxonomy

Kingdom- Animalia
Phylum- Arthropoda
Class- Insecta
Order- Hymenoptera
Family- Apidae
Genus- Bombus
Species- B. dahlbomii

Morphology

Commonly known as the Patagonian Bumblebee or 'the flying mouse', B. dahlbomii is widely known for its large size, coming in at nearly 2 inches. Aside from their definitive size, Patagonian bumblebees can be distinguished by the orange/ ginger coloration on their abdomen and thorax with a black underside (Cox, 2019). They also have distinct large black eyes as well as black or dark brown wings.

Distribution

They are found in the Patagonian range that extends through Argentina and Chile. This habitat is considered to be a desert or semidesert in some areas. There are semi-drought or drought-tolerant plants in this region, therefore most of the vegetation is scrub-like in nature (Gonzalez, 2021). However, near sources of water and in more temperate regions, the Patagonian region is home to fragmented forested areas where Patagonian Bumblebees can be found. These fragmented forests are losing biodiversity due to deforestation and invasive species, B. dahlbomii is naturally equipped to preserve these forests (C.L Morales et al.) As well as being the largest bumblebee in the world, B. dahlbomii is the only native species of bumblebee in South America (Polidori, 2014).

Habitat and Sociality

Patagonian Bumblebees are known to be primitively eusocial and live within existing cavities and follow traditional bumblebee behaviors with regard to habitat and sociality. In the spring, a queen will locate an empty cavity underground, such as preexisting bee nests or rodent holes. The queen will then go out to forage and after collecting enough resources, will return to the nest and build combs for pollen and the first beginnings of the brood. After the brood begins emerging, then more eggs are laid (including male drones to keep the population stable). Bumblebee nests are disorganized, unlike honeybee nests. Brood cells, honey, and pollen are all next to one another with no organization (Greenwood, 2019). This is directly related to their primitive eusociality. B. dahlbomii does not have rigid morphological castes, large colony sizes, and has dominance interactions that define it as primitively eusocial (Toth pg. 43, 2021).

Bumblebee nest, pictured above. No pictured documentation of B. dahlbomii nests, but they are known to be similar to traditional bumblebee nests.

Diet

Patagonian Bumblebees, like all other bumblebees, feed on nectar and nectar products collected from flowers. Their favorite flowers have been documented as the Chilean Bellflower as well as the Peruvian Lily (Cox, 2019). While documentation is limited on the primary diet of the Patagonian Bumblebee, it can be assumed that many other flowers are visited by this species.

Relationship with B. ruderatus and B. terrestris

B. dahlbomii is listed as endangered on IUCN Red List (IUCN, 2021) and its population continues to decline. The major cause of its decreasing population is due to competition with Bombus ruderatus and Bombus terrestris, two invasive species of bumblee introduced nearly 30 years ago to increase Trifolium (clover) production in the region. The introduced species are rapidly increasing in population and out-competing the Patagonian Bumblebee both for food as well as nesting sites. There are concerns that pollen transfer efficiency is reduced in B. ruderatus and B. terrestris due to their smaller body sizes (Morales, 2004). Pollen transfer is important in the Patagonian forests because B. dahlbomii is endemic to those forests, therefore having the highest efficiency. There is also evidence that these invasive species have brought parasites such as Apicysits bombi, which is yet another way B. rudderatus and B. terrestris have impacted the population of the Patagonian Bumblebee (The largest bumblebee).

B. terrestris, pictured top left. B. ruderatus, pictured bottom left.

Syrphid Fly Mimicry

The species of syrphid, Anierophora aureorufa, that is considered to be a Batesian mimic of B. dahlbomii (Smith-Ramierez et al). It mimics these bees in morphology, but no studies have been conducted on similarities in behavior, however syrphid flies are considered to be important pollinators. Very little information is known about A. aureorufa, however, it is also threatened by habitat loss and potential competition from non-native species.

References

“Bumblebees of the World . . . #1 Bombus Dahlbomii.” Bumblebee Conservation Trust, Registered Charity No. 1115634, 17 Jan. 2019, https://www.bumblebeeconservation.org/bumblebees- of-the-world-1-bombus-dahlbomii/.
IUCN 2021. The IUCN Red List of Threatened Species. Version 2021-2. https://www.iucnredlist.org. Downloaded on [1 Dec. 2021].
"The Largest bumblebee in the world- Bombus dahlbomii - Feat. Dr. Amy Toth - World bee day 2021" YouTube, uploaded by Inside the Hive TV, 20 May, 2020, https://www.youtube.com/watch?v=RU2Qzn0QmRY
Montalva, José, et al. "The Giant Bumble Bee (Bombus dahlbomii) in Mapuche Cosmovision." Ethnoentomology 4 (2020): 1-11.
Morales, C. L., and M. A. Aizen. "Potential displacement of the native bumblebee Bombus dahlbomii by the invasive Bombus ruderatus in NW Patagonia, Argentina." Proceedings of the 8th IBRA International Conference on Tropical Bees and VI Encontro sobre Abelhas, Ribeirão Preto, Brasil, 6-10 September, 2004. 2004.
Morales, Carolina L., et al. "Rapid ecological replacement of a native bumble bee by invasive species." Frontiers in Ecology and the Environment 11.10 (2013): 529-534.
Murúa, Maureen M. "Changes in wing length in the pollinator Bombus dahlbomii occurring with the fragmentation of the Maulino forest, Chile." (2011).
Patitucci, Luciano & Mulieri, Pablo & Mariluis, Juan. (2016). Taxonomic review of the species of Helina R.-D. (Diptera: Muscidae) from Andean-Patagonian forests. Zootaxa. 4150. 281- 313. 10.11646/zootaxa.4150.3.3.
“Photos of Bombus Dahlbomii · Natusfera.” Natusfera, https://spain.inaturalist.org/taxa/497142-Bombus-dahlbomii/browse_photos.
Polidori, C. & Nieves-Aldrey, J. Comparative flight morphology in queens of invasive and native Patagonian bumblebees (Hymenoptera: Bombus). Crit. Biol. 338, 126–133. https://doi.org/10.1016/j.crvi.2014.11.001 (2015).
Retrieved [12, 2, 2021], from the Integrated Taxonomic Information System (ITIS) on-line database, www.itis.gov, CC0 https://doi.org/10.5066/F7KH0KBK
Smith-Ramírez, Cecilia, Lorena Vieli, and Rodrigo M. Barahona-Segovia. "ANERIOPHORA AUREORUFA (PHILIPPI, 1865)(DIPTERA: SYRPHIDAE): A FLY SPECIALIZED IN THE POLLINATION OF EUCRYPHIA CORDIFOLIA CAV.(CUNONIACEAE R. BR.), AN ENDEMIC SPECIES OF SOUTH." Journal of Pollination Ecology 27.2 (2021): 28-35.
Toth, A. (2021) ENT358X Lecture 3 Sociality 2021 [PowerPoint presentation]. https://canvas.iastate.edu/courses/85607/files/16327528?module_item_id=4002824
Webb, Kempton E. and Díaz, Emilio Fernando Gonzalez. "Patagonia". Encyclopedia Britannica, 30 Jul. 2021, https://www.britannica.com/place/Patagonia-region-Argentina. Accessed 4 December 2021.

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