Bumblebees of the World Blog Series… #12 Bombus kluanensis
by Paul Williams, researcher at the Natural History Museum, London, and Darryl Cox, Senior Science & Policy Officer.
Our Bumblebees of the World journey ends in the Arctic Circle with one of the newest described bumblebee species to science, Bombus kluanensis, named after the Kluane Lake in the Yukon region of Canada.
Latin name: Bombus kluanensis
Common name/s: Kluane bumblebee
Colour pattern: Queens, workers and males broadly similar: mainly yellow, with a black band across the thorax at the wings, abdomen is yellow haired at the top, followed by a black tail or occasionally a black tail with an orange tip.
Favoured flowers: Unknown
Global region: Arctic
Geographic distribution: North America: Canada (Yukon) and U.S. (Alaska)
Conservation status: Not assessed
It is not very often in the 21st century that new bumblebee species are discovered. However thanks to molecular and morphological analysis by the world’s leading bumblebee experts, a brand new species was described to science in 2016. Bombus kluanensis, originally thought to be a variation of Bombus neoboreus was found to be genetically and morphologically distinct. Both species belong to the subgenus group known as Alpinobombus, an interesting group of bumblebees that can occur as far north in the Arctic as there are food plants available. Those that do inhabit the Arctic Circle are adapted to live with especially short cold summers and have larger bodies and longer hair to keep them warm. They might even be better at thermoregulation than other bumblebees, although this has yet to be investigated.
So how did Bombus kluanensis remain undiscovered for so long? In a recent assessment of the Alpinobombus group, Paul Williams and his colleagues note that the first specimens of this bumblebee species were two queens collected from the Klutlan Glacier in the Yukon, Canada, in 1913. It was not until 60 years later that these specimens were assigned the name Bombus strenuus (which would later be known as the Active bumblebee, Bombus neoboreus) in a review of bumblebees from the Western Hemisphere. A more extensive collecting effort was carried out in 1971 and 1972, in which 18 queens and over 200 workers were collected from Kluane, Yukon. These were also assigned the name Bombus stenuus upon review in 1986. They now reside in the Smithsonian collection in Washington DC, where they remained misidentified until 2015, when Paul re-examined them. What prompted Paul to re-examine these specimens was his discovery that two specimens, collected from the Saint Elias Mountains (Yukon) in 2010 by his colleague, Canadian Zoologist, Syd Cannings, were genetically distinct from other Bombus neoboreus. The DNA barcodes of the new species was later matched to other specimens found in the Alaska mountain range in the Denali National Park, Alaska, as well as the historical records from the Kluane region.
Since the discovery, Williams and Cannings have worked to find useful comparable morphological features which can be used to differentiate the Kluane bumblebee from the Active bumblebee. Some of the most useful features are a more extensively longer than broad cheek, more yellow hair with black hairs intermixed along the top two thirds of the thorax (the same area is very pale with few black hairs in Bombus neoboreus), a broad yellow band at the bottom of the thorax, and more black than orange hairs on the abdomen, compared to Bombus neoboreus.
The Kluane bumblebee has not yet had its conservation status assessed, however Syd, who works as Species at Risk Biologist for the Canadian Wildlife Service, explained some of the work that is going on in the region which should benefit the species:
“The government of Canada is interested in increasing the area of their protected areas, and doing this in a rational way that protects biodiversity, so they have given funding to the Wildlife Conservation Society to use the IUCN Key Biodiversity Area (KBA) protocol to delineate KBAs in Canada. The Yukon was selected as a test case for this protocol and we had a 2-day workshop in Whitehorse last month. Part of that protocol looks at endemic species where KBAs could hold more than 10% of the global population of a species (or in the case of a national KBA, more than 10% of the national population). One of the KBAs we looked at was Kluane National Park itself, and Bombus kluanensis was one of the endemic species that we used to justify mapping a KBA using the park boundaries. There are a number of species that are restricted to that region, presumably because of glacial refugia there during the Pleistocene.
Another area that we are interested in is Asi Keyi, a territorial park proposal to the north of Kluane, where we found Bombus kluanensis during a brief visit a few years ago. Yukon Parks is planning to fly into that area this summer, and we hope to hitch a ride in with them to look for endemic plants and insects, including Bombus kluanensis. Although I call this area a ‘proposed’ park, it really is more than that, since the area was identified by the Kluane First Nation in their final land claims settlement as a park. This means it will be a protected area, once all the agreements and plans are in order.”
Interestingly, the story does not end there. Further analysis of specimens collected from Alaska between 2015 and 2017 revealed a second group, ‘unnamed2’, which are genetically distinct from kluanensis, as though they might be a separate species. However, further research into these and other genes shows that these ‘unnamed2’ individuals each have two divergent forms of the COI barcode gene (the section of DNA commonly analysed to uniquely identify a species), a phenomenon that has not yet been widely reported in other bumblebees. For now, because B. kluanensis and ‘unnamed2’ do not show any geographic segregation, they are considered members of the same species, pending further investigation.
Links to further information
Natural History Museum species account
Natural History Museum Bombus – Bumblebees of the world homepage
IUCN Bumblebee Specialist Group
Acknowledgements
Many thanks to Syd Cannings for his helpful information.
Our position on managed honeybees
9 March 2020
The Trust has published a new position statement on managed honeybees. The statement has been prompted by concerns that, under certain circumstances, managed honeybees can have detrimental impacts on wild pollinator species, including bumblebees.
Our Senior Science & Policy Officer, Darryl Cox, provides the background on why we’ve decided to publish the statement.
Q1. What prompted the Trust to produce the position statement?
There is an increasing body of research which shows that, in some situations, beekeeping can have negative consequences for bumblebees (and potentially other pollinators) by increasing competition for food and by passing on diseases. These negative consequences are most marked in areas where there are fewer flowers or higher densities of honeybee hives, and could potentially be serious where vulnerable populations of wild bees are present. This statement aims to mobilise that research into action and highlights important steps that can be taken by beekeepers, conservationists, and anyone else with an interest in helping bumblebees, to lessen any potential negative impacts of managed honeybees.
Q2. Is all beekeeping bad for wild bees?
No. The message is not that beekeeping is bad, and it’s definitely not something we want to avoid or prevent. Our aim with this statement is to help inform people of best practice and encourage responsible beekeeping and well-thought-out hive placement. Keeping honeybees is important economically for honey and wax production, and for pollination of some crops and wild plants, as well as being firmly embedded in our culture. Several of the Trust’s staff and supporters are beekeepers, and are also some of the biggest advocates for wild bee conservation. The important bit is finding the middle ground that balances wild bee conservation and beekeeping, and making sure that rare wild bees aren’t inadvertently harmed.
Q3. What are the main recommendations?
The main recommendation is to take a precautionary approach to how we do beekeeping so that we do not accidentally end up causing problems for our wild pollinator communities. Five specific recommendations are made in the statement which outline how the precautionary principle can be applied in practice.
The position statement is available here.
Bumblebees of the World Blog Series… #9 Bombus gerstaeckeri
by Denis Michez, Researcher at Université de Mons, Belgium.
September’s blog features a vulnerable European bumblebee species, Bombus gerstaeckeri, and comes from Denis Michez, a researcher at Université de Mons, Belgium, who studies global bee diversity and conservation.
Latin name: Bombus gerstaeckeri
Common name/s: None
Colour pattern: Males and females ginger haired thorax that extends on to the top of the abdomen, the rest of which is black with a blonde/white tail (similar to Tree bumblebees, Bombus hypnorum)
Favoured flowers: Aconitums (eg. Monkshoods)
Global region: Palaearctic
Geographic distribution: Europe: Andorra, Austria, France, Germany, Italy, Romania, Russia, Slovenia, Spain, Switzerland, Ukraine
Conservation status: Vulnerable (at European level)
Of all the bumblebees described globally, only three species are described as oligolectic (specialists), which means they have a strong preference for a particular food source. Two species: Bombus consobrinus and B. gerstaeckeri are specialists on plants from the genus Aconitum (Ranunculaceae), which includes Monkshoods, and also B. brodmannicus delmasi, one of the two subspecies belonging to the species B. brodmannicus, shows some degree of oligolectism on the genus Cerinthe (Boraginaceae).
Given their morphological similarity and their food specialisation on Aconitum, it has long been thought that B. consobrinus and B. gerstaeckeri should be two sister species or even two subspecies of the same species. However, the publication of the bumblebee evolutionary history demonstrated that these two species are not sisters. Fascinatingly, the evolutionary event of food specialization on Aconitum plants therefore took place twice, independently. The actual sister species of B. consobrinus and B. gerstaeckeri are B. koreanus and B. supremus, respectively, two species with Asian distributions, which do not show the same specialisation.
Specialisation on plants with such deep flowers requires an extremely long proboscis (tongue).
Whereas B. consobrinus has a completely palearctic distribution from Norway to Japan, B. gerstaeckeri has a West-Palearctic distribution (Fig. 2) and mainly occurs in fragmented populations across mountainous regions. It is found in the Pyrenees, the Alps, the Carpathians and it is also present in the Caucasus. In the Ukrainian Pyrenees and Carpathians, populations are isolated and made up of a small number of individuals. Four observations in the Romanian Carpathians have also been recorded. When populations exist in isolation like this (Fig. 2), we sometimes find they become genetically distinct from each other over time, but in this case separate populations have remained broadly similar. They were however, more distinct than another more common species, the Garden bumblebee (B. hortorum), which is found across the same areas.
In the Alps and the Pyrenees, B. gerstaeckeri mainly visits the following Aconitum species: Anthora (A. anthora), Monkshood (A. napellus) and Wolf’s bane (A. lycoctonum). Several other food plants are occasionally visited by this species, such as Epilobium angustifolium or Delphinium dubium, probably for the nectar. It is not entirely clear why this specialisation has taken place, however it seems as though B. gerstaeckeri is reliant on pollen from Aconitum plants for larval development, which could be down to the nutritional content of the pollen, but there is also the possibility that toxins within the plants affect this species’ pollen foraging choice.
Links to further information:
Natural History Museum species account
Natural History Museum Bombus – Bumblebees of the world homepage
IUCN Bumblebee Specialist Group
References
Cameron SA, Hines HM, Williams PH, 2007. A comprehensive phylogeny of the bumble bees (Bombus). Biological Journal of the Linnean Society 91: 161-188.
Dellicour S., Michez D., Mardulyn P. 2015. Comparative phylogeography of five bumblebees: impact of range fragmentation, range size and diet specialisation. Biological Journal of the Linnean Society 116: 926-939.
Delmas R, 1962. Notes zoogéographiques et systématiques sur les Bombidae. I. – Le Bombus brodmannicus Vogt des Alpes françaises. Annales de l’Abeille 5(3): 175-179.
Delmas R, 1976. Contribution à l’étude de la faune française des Bombidae (Hymenoptera, Apoidea, Bombidae). Annales de la Société Entomologique de France (n.s.) 12: 247-290.
Konovalova I, 2007. The first record of the rare oligolectic bumblebee Bombus gerstaeckeri
Morawitz (Hymenoptera: Apidae: Bombini) from Ukraine. Annales de la Société Entomologique de France (n.s.) 43(4): 441-443.
Løken A, 1961. Bombus consobrinus Dahlbom, an oligolectic bumblebee (Hymenoptera, Apidae). Proceeding of the XIth Int. Congr. Ent. 1960 1: 598-603.
Løken A, 1973. Studies on Scandinavian Bumblebees (Hymenoptera, Apidae). Norsk Entomologisk Tidsskrift 20: 1-218.
Mahé G, 2008. Bourdons rares du Parc Naturel Régional du Queyras (Hautes-Alpes, France). OSMIA 2: 21-25.
Moczar M, 1953. Magyarország és a környezö területek dongóméheinek. (Bombus Latr.) rendszere és ökológiája, Magyar Nemzeti Múzeum. Termézettudományi Múzeum évkönyve (Annales Historico-naturales. Musei Nationalis Hungarici). Annales Historico-naturales Musei Nationalis Hungarici 4: 131-159.
Pittioni B, 1937. Bestäubung und Nektarraub beim Gelben Eisenhut (Aconitum vulparia Rchb). Aus der Heimat, Stuttgart 50: 209-213.
Ponchau O, Iserbyt S, Verhaeghe JC, Rasmont P, 2006. Is the caste-ratio of the oligolectic bumblebee Bombus gerstaeckeri Morawitz (Hymenoptera: Apidae) biased to queens? Annales de la Société Entomologique de France 42(2): 207-214.
Tkalců B, 1973. Taxonomie von Pyrobombus brodmannicus (VOGT) (Hymenoptera, Apoidea, Bombinae). Acta entomologica Bohemoslovaca 70 (4): 259-268.
Bumblebees of the World Blog Series… #10 Bombus brodmannicus
by Denis Michez, Researcher at Université de Mons, Belgium and contributor to the IUCN RedList assessment for several European bumblebee species.
This month Bumblebees of the World features Bombus brodmannicus, a poorly understood and endangered bumblebee species found in two fragmented populations separated by more than 2,500km!
Latin name: Bombus brodmannicus
Common name/s: None
Colour pattern: Queens, workers and males have two pale whitish-grey bands on thorax, a broad whitish band at top of abdomen and red tail.
Favoured flowers: Eastern population visits a variety of flowers including clovers. Western sub-species specialises on Cerinthe, although will also visit other plants for nectar, particularly the males.
Global region: Palaearctic
Geographic distribution: Europe, France, Italy, Asia Turkey, Armenia
Conservation status: Endangered (at European level)
In the east B. brodmannicus can be found in north east Turkey and Armenia across the Caucasian mountains, where it can be quite locally abundant. In the West, the subspecies B. brodmannicus delmasi is restricted to high altitudes in the southern French Alps and a small number of nearby locations in Italy. The species is found on southern slopes of the southwestern Alps in subalpine and alpine zones supporting large patches of Cerinthe, its main food plant. The species is active very early in the morning and at sunset.
Last month we talked about how only three species of all bumblebees worldwide are considered as specialists on a particular food plant. Interestingly, the eastern population of B. brodmannicus, located in the Caucasian mountains is a generalist, while the remote subspecies found in certain valleys of the Western Alps (map above), B. brodmannicus delmasi is considered a specialist. This specialism was deduced from field observations reporting a marked preference of the subspecies for Cerinthe minor L. and Cerinthe glabra . Despite the species reliance on pollen from Cerinthe, it is also known to visit other plants such as Calamintha, Cerinthe , Epilobium, Scabiosa, Echium, Nepeta, Knautia and Stachys for nectar. This behavior is particularly relevant for males whose life-cycle is partly offset from the flowering Cerinthe.
The restricted distribution and food specialisation led to an assessment as Endangered in the IUCN Red List of European Bees. Because of its highly specialised foraging requirements and its already localised distribution in a small area of the Alps, the western population seems extremely vulnerable to warming from climate change. On the other hand, the eastern population is rather widespread in the Caucasian region with no apparent food specialisation. It is therefore much less vulnerable to climate change.
Links to further information
Natural History Museum species account
Natural History Museum Bombus – Bumblebees of the world homepage
IUCN Bumblebee Specialist Group
References
Dellicour, S., De Jonghe, R., Roelants, D. and Michez, D. 2012. Oligolectisme de Bombus brodmannicus delmasi Tkalců (Hymenoptera, Apidae): observations et analyses. Osmia 5: 8-11.
Delmas, R. 1976. Contribution à l’étude de la faune française des Bombidae (Hymenoptera, Apoidea, Bombidae). Annales de la société entomologique de France (N.S.) 12: 247-290.
Franzén, M. and Molander, M. 2012. How threatened are alpine environments? a cross taxonomic study. Biodiversity Conservation 21: 517-526.
Franzén, M. and Ockinger, E. 2011. Climate-driven changes in pollinator assemblages during the last 60 years in an Arctic mountain region in Northern Scandinavia. Journal of insect conservation 16: 227-238.
Goulson, D., Lye, G.C. and Darvil, B. 2008. Decline and conservation of bumble bees. Annual Review of Entomology 53: 11.1–11.18.
Iserbyt, S. and Rasmont, P. 2012. The effect of climatic variation on abundance and diversity of bumblebees: a ten years survey in a mountain hotspot. Annales de la Société entomologique de France (N.S.) 48(3-4): 261-273.
IUCN. 2015. The IUCN Red List of Threatened Species. Version 2015.1. Available at: www.iucnredlist.org. (Accessed: 28 May 2015).
Rasmont, P. and Iserbyt, I. 2010-2012. Atlas of the European Bees: genus Bombus. STEP Project. Atlas Hymenoptera. Mons Available at: http://www.zoologie.umh.ac.be//hymenoptera/page.asp?ID=169.
Rasmont, P. and Iserbyt, S. 2012. The Bumblebees Scarcity Syndrome: Are heat waves leading to local extinctions of bumblebees (Hymenoptera: Apidae: Bombus)? Annales de la Société entomologique de France (N.S.) 48(3-4): 275-280.
Tkalcu, B. 1973. Taxonomie von Pyrobombus brodmannicus (Vogt) (Hymenoptera, Apoidea, Bombinae). Acta entomologica bohemoslovaca 70(4): 259-268.
Williams, P.H., Colla, S.R. and Xie, Z. 2009. Bumblebee vulnerability: common correlates of winners and losers across three continents. Conservation Biology 23: 931-940.
Bumblebees of the World Blog Series… #11 Bombus veteranus
by John Smit, researcher at European Invertebrate Survey – the Netherlands / Naturalis Biodiversity Center, the Netherlands.
This month guest author, John Smit, discusses the conservation of the Sand-coloured carder bee (Bombus veteranus) in the Netherlands, a species which has experienced widespread declines across the country.
Latin name: Bombus veteranus
Common name/s: Sand-coloured Carder bee
Colour pattern: Very constant, all yellowish grey (sandy coloured) with a black thoracic band and thin bands of black hairs on abdominal segments 3-5 in queens and workers and 3-7 in males. Freshly emerged specimen can have bright yellow hairs on the second abdominal segment, especially queens.
Favoured flowers: Red clover, white clover, common comfrey and, to a lesser extent, common bird’s-foot trefoil and water mint. Males can frequently be found on Asteraceae like creeping thistle and goldenrod, but also on sea holly (Apiaceae).
Global region: Entire Palearctic, from western France to the Siberian pacific coast, not present in the Mediterranean part of Europe, nor in England
Geographic distribution: Europe: Austria, Belarus, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Latvia, Lithuania, Luxembourg, the Netherlands, Poland, Romania, Slovak Republic, Sweden, Switzerland, Ukraine. Asia: Russia up to the Pacific coast, including Altai and Sayan mountains and northern Mongolia.
Conservation status: Least Concern
Bombus vetranus is mainly found in the plains of northern Europe, in the southern parts it is confined to slightly higher elevations, with the French Central Massif as the southernmost record. It has disappeared over much of its distribution over the last 100 years, leaving it patchily distributed at present. This is well documented in the Netherlands, where it occurred throughout the country up until the 1970’s, followed by a steep decline. At present it is known from only two areas, along a river and a former estuary.
Evidently, it needs large, open and flower rich areas. The extensive agricultural areas in the Netherlands provided a suitable habitat for this species until agricultural intensification was introduced followed by the use of fertiliser. The borders between the smaller fields and meadows, often consisting of hedgerows, made way for barbed wire and the clover-fields used as a natural fertiliser all but disappeared. There seems to be a strong link between the disuse of red clover as a natural fertiliser and the sharp decline in some of the bumblebee species in the Netherlands. In fact, recent pollen-analyses on Bombus veteranus revealed a strong preference for both red and white clover, as well as common comfrey. Comparison of the pollen load of museum specimens with those of recent specimens revealed a shift in quantity from 64% of both red and white clover together in museum specimens to just 27% in 2017. Conversely common comfrey increased from 24% to 61%, though there are noted differences between the three recent localities surveyed, ranging from 46% at Tiengemeten to 71% at the Biesbosch.
Bombus veteranus is a late appearing species, with queens emerging from hibernation in the end of April or beginning of May and the first workers typically appearing around June, at least in the Netherlands. This is a disadvantage regarding nesting places, compared to the much more common earlier emerging species. It is reported in the literature that nesting typically occurs on the surface, amongst tall grasses or mosses, but can also be underground. The one nest recently found in the Netherlands was situated underground (video below). It consisted of a clump of cells the size of a man’s fist, with no more than 200 to 250 cells. Inside the nest two larvae of the hover fly Volucella bombylans were found, which live as scavengers at the bottom of the nest.
A species action-plan was drawn up for the Netherlands, with measures at the population level. The main goals are to reconnect the two remaining distribution areas and to provide the means for Bombus veteranus to return to the agricultural areas in the Netherlands, where this species can be used as an indicator, or an umbrella species for a more sustainable agricultural system.
Should you take a bumblebee home?
by Jack Reid, Outreach and Volunteering Officer at Bumblebee Conservation Trust
So, you kidnapped a bumblebee…
Each year, the Trust receives dozens of e-mails and phone calls from well-intentioned beenappers who have been out and about and found a tired-looking lone bumblebee that they’ve rescued and taken home with them to care for. In case you’ve been considering the practicalities of taking a bumblebee home, we have written up this useful guide to caring for your new friend, without taking it home!
Should I take a bumblebee home?
No! Bumblebees have their own homes.
At all times throughout the year, bumblebees have important jobs to be doing – whether it’s queens who are searching for a nest site or gathering pollen for their first clutch of workers; workers who are out, working hard to gather enough pollen and nectar to support their queens and siblings; or males who, despite their work ethic, are vital to ensuring there is a next generation of bumblebees.
For this reason, it’s very important to leave the bumblebees to what they’re supposed to be doing – they can’t support their nests if they can’t get back to them!
What should I feed bumblebees?
Bees need flowers!
Bumblebees are exceptional at identifying the nutrients and foods they need when they are foraging on flowering plants out in the wild. Our knowledge of bumblebee feeding habits is constantly evolving – but nobody knows what they need better than the bumblebees themselves. So we recommend that, rather than taking a tired-looking bumblebee home, you first consider whether they are in danger where they are, or if they’re simply resting!
For more information on if and when to move bumblebees, and when and what to feed them, please click here.
When should I release them?
The best time to leave your bumblebee alone was before you picked them up. The second best time is now!
Bumblebees navigate using landmarks, like buildings, or rocks, or trees. If they can’t find locations that they recognise, they may struggle to find their way back home to their nest when you release them.
If possible, bumblebees should be released near to where you found them. If not, placing them outside on or near to flowering plants is the next best option.
So what do I do if I find a tired bumblebee?
This is a great question – for information on what to do if you find a tired bumblebee, and when to feed, and/or possibly relocate them, please click here.
Bumblebees of the World Blog Series… #8 Bombus eximius
By Chawatat Thanoosing, PhD student and Paul Williams, researcher at the Natural History Museum London
This month we’ll explore a deep montane tropical forest in Asia, where Chawatat Thanoosing— a PhD student at Imperial College London and the Natural History Museum—is doing his research on the ecology of tropical bumblebees, to see the remarkable giant bumblebee, Bombus eximius.
Latin name: Bombus eximius
Common name/s: Orange-legged bumblebee
Colour pattern: Whole body mainly black with brightly orange tail and legs in all castes.
Favoured flowers: Mid altitude flowering shrubs and trees, and wild orchids
Global region: Oriental region
Geographic distribution: Asia: India, Nepal, Bhutan, Bangladesh, Myanmar, Thailand, Vietnam, China, and Taiwan
Conservation status: Not evaluated
The impressive Bombus eximius is a broadly distributed Asian bumblebee, found across the Himalayas, Southern China, Taiwan island and in the mountain ranges of northern Southeast Asia, at mid altitude, from approximately 1000 m above sea level. Unlike common bumblebees in Europe (eg. B. terrestris), which show black and yellow striped patterns on their abdomen, B. eximius is often a predominantly black bumblebee with orange on their tail and legs, although sometimes the populations in Southern China and Taiwan have extensively orange abdomens as well.. This orange-colouring across the legs is in congruence with the original subgeneric group that this species was attributed to, Rufipedibombus, which means red-legged bumblebees, although it is now included as part of Melanobombus, distantly related to the European B. lapidarius.
Queens of B. eximius are some of the largest bumblebees in the world. The body length of the queen is approximately 3 cm long, similar in size to the Patagonian bumblebee, B. dahlbomii, in South America. Strangely, those big bumblebees show almost the opposite colour pattern between them. They have an orange thorax and abdomen with black legs, whereas B. eximius often has a a black body and orange legs. The two species have evolved independently in different lineages and different geographic regions.
The food preference of B. eximius has rarely been studied. In Thailand, this species has been reported visiting and pollinating some native orchids: Dendrobium infundibulum and Cymbidium insigne. Care is needed when identifying these bees because B. eximius is mimicked very closely by B. flavescens, a relative of B. pratorum. When B. eximius lands on an orchid flower, pollinia (a sticky orchid pollen mass) will either attach to its thorax (in D. infundibulum flowers) or abdomen (in C. insigne flowers). The cross-pollination of the orchids occurs when the bumblebee with attached pollinia visits another orchid flower. In addition, at Doi Inthanon mountain, the highest peak in northern Thailand, B. eximius has been observed to visit Hooker’s St. John’s Worts (Hypericum hookerianum), Som Pae (local Thai name for Vaccinium exaristatum), Rubus chevalieri and Saurauia napaulensis for food.
The IUCN conservation status of this bumblebee has not yet been assessed. This species still flies and hides in the shady forests of the mountains. Despite extreme deforestation, land use changes and heavy pesticide use in this region, no one knows whether the population of this bumblebee is decreasing or not. From the obvious changes in the environment, raising awareness and protecting bumblebees in this region are likely to be urgently needed.
Links to further information:
Natural History Museum species account
Natural History Museum Bombus – Bumblebees of the world homepage
Bumblebees of the World Blog Series… #6 Bombus rupestris
by Darryl Cox, Senior Science & Policy Officer
Bumblebees of the world would not be complete without delving into the darker side of bumblebee life, and so this month features one of around thirty described parasitic cuckoo bumblebees, the Red-tailed cuckoo (Bombus rupestris).
Latin name: Bombus (formerly Psithyrus) rupestris
Common name/s: Red-tailed cuckoo, Hill cuckoo
Colour pattern: In Britain, females are black with red tails, similar to their host species, the Red-tailed bumblebee (B. lapidarius). However Red-tailed cuckoos are much sparser haired, lack pollen baskets, have large box shaped heads and distinctive black/blue wings. Some females have a faint yellow band which can be seen at the collar. Males can be variable, however usually have a faint yellow collar and bands across the midriff of the lower thorax and upper abdomen, with a red tail. Yellow-banded female forms are found in Asia.
Host species: Red-tailed bumblebee (Bombus lapidarius), Bombus sichelii and likely other species from the subgenus Melanobombus
Favoured flowers: In spring – dandelions, comfrey, oxeye daisies. New females and males in summer – thistles ragwort, brambles and other garden plants like lavender.
Global region: Palaearctic, Oriental regions
Geographic distribution: Europe – Albania, Andorra, Austria, Belarus, Belgium, Bosnia and Herzegovina, Bulgaria, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Lithuania, Luxembourg, Republic of North Macedonia, Moldova, Montenegro, Netherlands, Norway, Poland, Romania, Russia, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Ukraine, United Kingdom. Asia – Turkey, Russia, Kazakhstan, Mongolia, Tibet, China.
Conservation status: Least concern
For those that have not heard of cuckoo bumblebees before, they are a fascinating group of bumblebees which have evolved to take advantage of the hard-working nature of social bumblebees. Unlike social bumblebees, cuckoos have no workers of their own. Instead the cuckoo female invades the nest of a social species and either kills or enslaves the resident queen, before using the resident workers to collect food and help her raise her own brood.
In this case (in Britain), the Red-tailed cuckoo will emerge from hibernation between April and June, around six weeks after the first social Red-tailed bumblebee queens have emerged and started setting up their colonies. Timing is key in the world of the cuckoo bumblebees as they search out an established nest. They want to take over a nest which has grown strong enough to raise as many offspring as possible, without being too strong for the cuckoo female to gain control. Once she finds a nest, the cuckoo lies in wait and often digs down into the nest material whilst trying to remain unseen. It is thought she does this to try and take on the scent of the nest, and perhaps to wait for the ideal time to make her move. If the workers and their queen find her, they will attempt to kill her or at very least evict her from their territory. This is the fate for many cuckoo females and nests are often strewn with the carcases of failed usurpers. Nest-stealing behaviour is not limited to cuckoo species though, and many later emerging social queens will also attempt to take over nests of other bumblebees to gain an advantage.
Cuckoos, however, have evolved to be nest-stealing specialists, built for fighting, and once in a position to enter a nest with minimal challenge, they use this to their benefit. Harder exoskeletons, the segments of which fit tightly together (unlike social bumblebees which excrete wax from these points), more powerful mandibles, and a longer sting eventually prove too much for the founding queen, and if she is not killed off she may become subservient to her oppressor, acting in the same manner as her daughter workers.
The workers she leaves behind will continue to forage and provide for the nest, however they will be helping to rear the cuckoo’s brood. The new cuckoo queen keeps her recently acquired workforce in check with the use of pheromones and aggressive behaviour. Any remaining eggs and young larvae are promptly destroyed, although those that are close to adulthood are spared to join the workforce. Some of the original workforce may go rogue and start to lay their own unfertilised eggs, however the new overlord is able to test the eggs to check if they are smooth or ridged. All cuckoo eggs are ridged, which is a useful characteristic for the policing intruder. Any smooth eggs are swiftly devoured. Unlike their social counterparts which lay between 8 and 16 eggs per clutch, cuckoos can lay batches of up to 20-30 eggs at a time, which is important as they only have a limited period of time before their workforce dies off. These eggs are reared into new male and female cuckoos, which then leave the nest to find a mate, before the fertilised females go into hibernation. The cycle then repeats itself in the following season.
After learning about this bumblebee underworld, many people decide they do not like cuckoos and we are often asked if anything should be done to prevent them from invading bumblebee nests. Some people have even gone as far as to devise novel nesting boxes aimed at preventing cuckoos from entering. However, this is not necessary or advisable. It is important to remember that these social parasites are intrinsic parts of nature too and several species are now critically rare due to unrelated declines in their host species. Human-caused drivers of population declines like habitat loss, pesticide use, disease and climate change are the things we should focus on tackling, rather than these naturally evolved brood parasites. There is so much more to discover about these intriguing invaders, but maintaining healthy bumblebee populations by addressing those human-caused problems is key.
Links to further information:
Natural History Museum species account
Natural History Museum Bombus – Bumblebees of the world homepage
IUCN Bumblebee Specialist Group
Richard Comont’s RSPB Spotlight bumblebees (2017)
Acknowledgements
Many thanks to Paul Williams of the Natural History Museum, London, for his help and advice.
Bumblebees of the World Blog Series… #7 Bombus inexspectatus
by Darryl Cox, Senior Science & Policy Officer
July’s Bumblebees of the world blog features the endangered Bombus inexspectatus, literally an unexpected European bumblebee, first described by Tkalcu in 1963, which has been found to parasitize on the Red-shanked carder bee (Bombus ruderarius). This species is one of two bumblebees, outside of the typical cuckoo bumblebee group (discussed in last month’s blog) to have evolved a parasitic way of life.
Latin name: Bombus inexspectatus
Common name/s: Unexpected bumblebee
Colour pattern: Males and females have two yellow bands on the thorax, a yellow band at the top of the abdomen and a red tail. The host species (Bombus ruderarius) mainly occurs with similar pattern to the British type (unbanded with a red tail), but can also have similar banding to the Unexpected bumblebee, although the back of the head is larger in B. inexspectatus than B. ruderarius in both males and females.
Host species: Red-shanked carder bee (Bombus ruderarius)
Favoured flowers: Females have been found on Clovers and Rampions, males on Knapweed and Thistles
Global region: Palaearctic
Geographic distribution: Europe – Alpine regions of France, Switzerland, Austria and Italy, and a disjunct population in the Cantabrian Mountains of Spain.
Conservation status: Endangered
When Tkalcu first made his discovery of a new/overlooked European bumblebee species it prompted European bumblebee specialists to resample potential locations and look back in their own collections to reassess potential specimens. As a result, the original four records soon became eighty or so. Interestingly, the original records included two males and two supposed workers, which happen to be the only two workers ever found for this species. The status of these females as workers was called into question by Yarrow in 1970 who proposed that inexspectatus could potentially be a social parasite of the closely-related Red-shanked carder bee (B. ruderarius), which he always found in good numbers wherever inexspectatus was found. He argued that the workers were merely ‘runt’ females which were underdeveloped in comparison to the rest of the female specimens. Close examination of collected specimens revealed that unlike social bumblebees and similar to cuckoos, inexspectatus specimens do not appear to secrete wax from their abdominal segments, which is an essential part of colony building among the social bumblebees. Yarrow noted that none of the specimens he had seen had any evidence of pollen collecting, and that the structures on the legs associated with pollen collection seemed to have degenerated slightly in comparison with social bumblebees, although not to the same extent as the main cuckoo group (Psithyrus subgenus).
It was not until 2005, when Andreas Muller and colleagues stumbled upon a Bombus ruderarius nest in the Swiss Alps, that Yarrow’s suspicions were supported with the first and only evidence of parasitism by inexspectatus. The nest they found was close to completion with no stored nectar, eggs or larvae, a selection of empty cocoons from various generations of workers and four unhatched cocoons, which four ruderarius queens later emerged from. No founding queen/females of either species were found, however two ruderarius workers, two males and one new queen remained in the nest when it was found, as well as one fresh inexspectatus female. This indicated that both the social queen and the parasitic female were co-existing in the nest, which has been found when other cuckoo bumblebees invade nests, but often the social colony does not successfully produce new queens or produces fewer than normal. As this is the only nest that has been found to date – we do not know how common it is for the two species to co-exist or if the invading bees manage to completely take over nests in the same way that some other cuckoo bumblebees do. There are also larger questions about this species’ general ecology and life history still to be answered, for example, whether inexspectatus can invade the nests of other hosts, similar to the other known parasitic bumblebee species.
Links to further information:
Natural History Museum species account
Natural History Museum Bombus – Bumblebees of the world homepage
IUCN Bumblebee Specialist Group
Acknowledgements
Many thanks to Maurizio Cornalba of the University of Pavia, Italy, and Paul Williams of the Natural History Museum, London, for their help and advice.
