by Darryl Cox, Senior Science & Policy Officer

The Southern Plains bumblebee (Bombus fraternus) features in this month’s Bumblebees of the World blog, with a particular focus on how the species’ endangered conservation status was classified by the  IUCN’s Bumblebee Specialist Group (BBSG).

Fact File

Latin name: Bombus fraternus

Common names: Southern Plains bumblebee

Colour pattern: Queens and workers are predominantly pale straw-coloured yellow with a black band between the dark wings and an extensive black tail. Males look similar, although can be more extensively yellow between the wings and have very large eyes.

Favoured flowers: Milkweed (Asclepias), Prairie clovers (Dalea), Blazing stars (Liatris), Sweet clovers (Melilotus), Prairie coneflowers (Ratibida) and Goldenrod (Solidago)

Global region: East Nearctic region, West Nearctic border

Geographic distribution: North America – Central to South-eastern US (Virginia, Texas, Minnesota, Massachusetts, Louisiana, Kansas, Iowa, Indiana, Illinois, Georgia, Florida, Colorado, Arkansas, Alabama, Mississippi, Missouri, Nebraska, New Jersey, New Mexico, North Carolina, North Dakota, Ohio, Oklahoma, South Carolina, South Dakota, Tennessee)

Conservation status: Endangered

The Southern Plains bumblebee is found to the east of the Rockies, across the prairie lands in the south of the Great Plains, stretching to the coastal plains of central Florida and New Jersey. With pale yellow and black banding, this short-tongued bumblebee has a similar colour form to a number of North American species, however it is has a very distinctive look, with extremely short and even hair across its body. This gives the bee a very close-cropped and neat look overall – almost like a bumblebee with a (forgive me) buzz cut! Some of the hair on the abdomen is completely flattened to the body making the abdomen look slim and sleek in comparison to other fuzzier bumblebees.

The IUCN-BBSG last assessed the conservation status of this species in 2014, when it was classified as endangered. Their justification came down to three main factors – relative abundance, which is a measure of how many records of this species there are in relation to the total number of species recorded, a change in its extent of occurrence, which relates to the species’ overall distribution, and the loss of suitable habitat within the species’ known range.

The IUCN-BBSG team took historical national bumblebee records and plotted the Southern Plains bumblebee’s relative abundance at 10 year intervals to understand how it had changed from 1912 to 2012. The figure below shows a historical downward trend which is close to being statistically significant. If the trajectory were to continue at this rate, the assessors warn the species could potentially be extinct within the next 80-90 years.

The decline in relative abundance since 2002 was consistent with a decline in distribution. The team mapped historical records and compared them with records post 2002 to understand the extent that the species still occurs across its known range. After taking care to avoid statistically overestimating range loss (by randomly rarefying the much larger number of pre-2002 records), they found that the species had reduced its area of occupancy by 28.62% since 2002. A heat map depicts the amount of surveying that took place between 2002 and 2012. This shows that some of the areas the species has declined from have also been well surveyed in recent times, which gives the team confidence in their assessment that Bombus fraternus has declined in range.

The third area of justification relates to severe changes that have occurred in the Southern Plains bumblebee’s habitat range, particularly since 2002. This period has seen native grasslands converted into agricultural land and increased use of agricultural pesticides. Identifying the negative impact that these changes have had is useful as it helps indicate what needs to change for this species to recover. The IUCN-BBSG identify the following general actions to conserve Bombus fraternus: restoring, creating and preserving natural grasslands, restricting harmful pesticide use within or close to their habitats, and protecting them from diseases introduced by managed bees.  However, more research is needed to fully understand the specific requirements of this distinctive species and how best to help it. For those wishing to get involved with Bumblebee Conservation in the U.S. check out the IUCN Bumblebee Specialist Group.

Links to further information:

IUCN Redlist page

Natural History Museum species account

Natural History Museum Bombus – Bumblebees of the world homepage

The Bumble bees of North America: An Identification guide. By Williams, P.H., Thorp, R.W., Richardson, L.L. and Colla, S.R. (2014) Princeton University Press, Princeton

IUCN Bumblebee Specialist Group

Xerces Society Bumblebee conservation page

Acknowledgements

Many thanks to Paul Williams of the Natural History Museum, London, for his help and advice.

by Paul Williams, Researcher at the Natural History Museum, London, and Darryl Cox, Senior Science & Policy Officer.

This month, Bumblebees of the world returns from across the Atlantic to feature Cullum’s bumblebee (Bombus cullumanus), a Eurasian species which is sadly no longer found in the UK and has experienced drastic declines across the rest of Western Europe.

Latin name: Bombus cullumanus

Common name/s: Cullum’s bumblebee

Colour pattern: In Western Europe, queens and workers are black with red tails and look very similar to Red-tailed bumblebees (B. lapidarius), although queens are smaller and sometimes have a very faint yellow band that can be seen at the collar.

Males have a dull yellow collar and bands across the lower thorax and majority of the upper abdomen with a red tail (similar to some brighter Ruderal bumblebee (B. ruderarius) males).

Favoured flowers: older male specimens are described as feeding on Knapweed, White clover, Wild marjoram, Musk and Dwarf thistles. Workers are thought to favour legumes.

Global region: Palaearctic

Geographic distribution: Europe – Moldova, Montenegro, Romania, Russia, Serbia, Spain, Ukraine. Asia – Russia, Turkey, Armenia, Iran, Afghanistan, Uzbekistan, Turkmenistan, Tadzhikistan, Kyrgyzstan, Kazakhstan, China, and Mongolia.

Conservation status: Critically Endangered in Europe

Cullum’s bumblebee, named after 7th Baronet, Sir Thomas Cullum, a medical doctor and well-respected natural historian from Suffolk, was described as new to science by William Kirby in 1802 after an interesting striped and red-bottomed male was spotted in Suffolk. It was not until 1926 that the connection was made between the yellow-banded males and the black females with red tails, which are difficult to separate from the similar, more widespread Red-tailed bumblebee (Bombus lapidarius).

Bombus cullumanus belongs to a broader species group of closely related species known as the cullumanus­-group. The species group has been the source of much debate amongst taxonomists and there have been several interpretations of the number of species within the cullumanus-group, but DNA barcoding has been able to provide a much clearer answer.

It turns out that Cullum’s bumblebee can be exceptionally variable in terms of colour pattern and because of this it has been classified as several separate species from different geographic locations. Williams et al. (2012) set out to sequence the DNA of some bumblebee specimens within the cullumanus-group and found that four bumblebees which had been classified as separate species are actually parts of Bombus cullumanus, which is known to be declining steeply in Western Europe (described in the fact file). The following ‘species’ have therefore been reclassified as parts of Bombus cullumanus:

• Bombus serrisquama – a yellow banded bumblebee found in Spain, Russia and Central Asia
• Bombus apollineus – a white banded bumblebee found in Turkey and Armenia.
• Bombus tenuifasciatus – darker yellow bands found in Central Asia
• Bombus nigrotaeniatus – also Central Asia and with no yellow band on the abdomen

The last confirmed sighting of Bombus cullumanus in the UK was a male on the Berkshire downs in 1941, making it one of two species that have likely gone extinct from the UK in the last 80 years (the other being the Short-haired bumblebee, Bombus subterraneus). It has similarly vanished from the Netherlands, Belgium, France, Germany, Sweden and Denmark.

Although this is undeniably sad news, the new understanding that the species is much more widely distributed than initially thought (albeit in different colour forms) means that in conservation terms, it is doing better than initially feared, especially in Russia and Central Asia where it can be common in grasslands. In fact, the genetic work by Williams and colleagues indicated that another species within the wider cullumanus-group, Bombus unicus, may actually be worse off. They are calling for urgent surveys to help assess the status of Bombus unicus, which seems restricted to the far East of Russia and has only ever been found in very low numbers.

Links to further information:

IUCN Redlist page

Williams, P.H., Byvaltsev, A., Sheffield, C., Rasmond, P., Bombus cullumanus—an extinct European bumblebee species? Apidologie (2013) 44: 121.

Natural History Museum species account

Natural History Museum Bombus – Bumblebees of the world homepage

IUCN Bumblebee Specialist Group

by Darryl Cox, Senior Science & Policy Officer

There are around 250 species of bumblebees across planet Earth, stretching across most of the Northern Hemisphere, from the arctic, right down to the southern-most tip of South America in the Southern Hemisphere. Each bumblebee species has a different distribution and all are an important part of life within their ecosystems. By transferring pollen that helps plants set fruit and reproduce, they are involved in the base layers of numerous food chains, which provide food and shelter for a great multitude of living things (including ourselves).

This year, we have decided to show our appreciation for some of the most beautiful and diverse bumblebees from across the world in our monthly Bumblebees of the World blog series, and what better way to start our series than with one of the world’s largest and most iconic bumblebees: Bombus dahlbomii.

Fact File

Latin name: Bombus dahlbomii

Common names: Patagonian bumblebee, Flying Mouse

Colour pattern: Deep orange/ginger thorax and abdomen, with black underside, legs and wings. (Queens, workers and males)

Favoured flowers: Chilean bellflower (Lapageria rosea), Peruvian lily (Alstroemeria aurea)

Global region: Southern Neotropical, Eastern Neotropical

Geographic distribution: South America – Chile, Patagonia, Argentina

Conservation status: Endangered

by Darryl Cox, Senior Science & Policy Officer

This month our bumblebee world tour stays in South America, although we are heading north from Patagonia into the Amazon basin, where our species in the spotlight is the Amazonian bumblebee, Bombus transversalis.

Fact File

Latin name: Bombus transversalis

Common names: None

Colour pattern: Queens and workers are black with two bright golden-yellow bands on the thorax, one yellow band towards the rear of the abdomen and a black tail. Males have similar banding, although the yellow is paler and the bands are more extensive on the thorax.

Favoured flowers: Unknown

Global region: Western Neotropical, Eastern Neotropical

Geographic distribution: South America – Brazil, Bolivia, Colombia, Ecuador, Peru

Conservation status: Least concern

18 February 2019

by Rosie Earwaker from Buglife, Back from the Brink’s Shrill Carder Bee Project Officer

Hints of spring are in the air. Bulbs are peeking up through the soil, with plenty of snowdrops, daffodils and crocus already in flower. Sightings of Buff-tailed bumblebees in gardens are more and more frequent as the days grow longer. It won’t be long now until different bumblebee species join them, although we will have to wait a couple more months until the high pitched buzz of our Shrill carder bee returns. It certainly won’t be a silent spring this year, but where will we be in 100 years’ time?

You may have seen the headlines recently about a study predicting that we could lose 41% of the world’s insect species in the next few decades. If the rate of loss continues, this could mean that within a century there will be a very small proportion of insects left on the planet. This is staggering and would be catastrophic to life on earth.

To those of us who study insects, this so called “insectageddon” is sadly nothing new; study upon study has been documenting these declines for years, decades even. However, this recent review paper has gone one step further, bringing all of this research together to really put a spotlight on the challenges we are currently facing. Habitat loss, pesticides and climate change are some of the main factors driving these extinctions. So what can be done?

We need to start taking biodiversity loss more seriously. This isn’t just for the politicians at Westminster and across the globe to action; you can also make a difference. From planting pollinator friendly plants and ditching the slug pellets, to shopping for more local, seasonal produce. Small actions can make a big difference.

Headlines like this highlight the importance of initiatives like Back from the Brink and the work of wildlife conservation organisations such as Buglife helping the “small things that run the planet”. There are plenty of ways to get involved with Back from the Brink, including volunteering opportunities. We are always keen to have more people on the look out for Shrill carder bee and helping to monitor bumblebees through the BeeWalk Scheme, which is vital to our understanding of how these creatures are faring.

Keep an eye out for forthcoming bumblebee identification training courses and lots of exciting surveys over the spring and summer. I start this year with a reinvigorated passion for saving our precious insects and I hope you do too.

By Elizabeth Franklin, Bumblebee Researcher, Guelph, Canada

This month’s Bumblebees of the World blog is written by Bumblebee Researcher, Elizabeth Franklin, from the University of Guelph, who focuses on the plight of a critically endangered bumblebee in North America.

Fact File

Latin name: Bombus affinis

Common names: Rusty patched bumblebee

Colour pattern: Workers, queens and males have a yellow collar, black band or circle followed by another yellow band on the thorax. Workers and queens have two, mostly yellow bands at the top of the abdomen whereas males have a rusty patch on the top of their abdomen giving the species its name.

Favoured flowers: Generalist but reported on hyssops, prairie clovers, sunflowers, blueberries, the apple family and goldenrods.

Global region: East Nearctic region (North American temperate region)

Geographic distribution: Canada (Ontario), United States (Wisconsin, Virginia, Tennessee, Ohio, Iowa, Indiana, Illinois, Connecticut, Maryland, Massachusetts, Minnesota)

Conservation status: Critically Endangered

By Cathy Horsley, Conservation Officer West Country Buzz

This summer, I learnt that different species of male bumblebees have different scents. I use a marking cage to examine bumblebees on my surveys to get a good close up look to identify them, and the male bees sooner or later released a puff of perfume.

Red-tailed bumblebees and Early bumblebees have a pleasant citrus smell, whereas the Buff-tailed bumblebees are more like smelly feet!

The odour comes from the release of pheromones, which are chemicals used to attract queens. By having their own distinctive aroma, males can be sure of attracting females from the same species.

Ever since Darwin’s day, and even earlier, male bumblebees have been observed following a set flight path. They tend to follow a linear circuit and pause at various places along the route to deposit a drop of pheromone. It has been noticed that males will temporarily leave their flight path, often in the early afternoon, to refuel on flowers. Different species will fly at different heights, or at different times of day, which also helps males to find the right species of female. By attracting queens to a particular place, males also avoid trying to mate with workers. Patrolling males on the lookout for queens is a fascinating subject, not least because although this is often observed, mating is rarely seen.

17 November 2017

By Ron Rock, Bumblebee Conservation Trust Volunteer

And so, we reach the end of another bee year. As I write, there are just a few Common carder bees still in the garden. The Red mason and Leaf-cutter bees are long gone but mud and leaf filled tubes in the bee nesters are evidence that their work has been done. Another generation is already in place and will emerge next spring and summer. But will it? Are bee nesters a fit and forget option in our gardens? Will the bees emerge and happily go on year after year? Sadly, the answer is probably not.

By attracting these bees to our gardens, we are encouraging them to nest in far higher densities than would occur in nature. As a consequence, parasites find bee nesters just as welcoming as the bees themselves. Left unchecked, pests and disease can completely wipe out your bee nester population in a relatively short period of time. It should be our duty to open, inspect, clean, and replace used nesting tubes annually to ensure the health of our solitary bee guests.

The ‘unwanted guests’ in the bee nesters include mites, flies and parasitic wasps which can all have a highly detrimental effect on the intended occupants. No matter how well maintained, bee nesters will attract a certain amount of unwelcome attention during the course of a season.

When all of the activity has ceased, I move my nesters into a sheltered part of the garden to protect them from rain and to allow the bees to pupate and metamorphosise into adult bees to take place. In nature, the bees would remain quiescent in their cocoons until spring, but at this point I step in and give them a helping hand. I use a combination of routed out trays, cardboard tubes with paper liners and — although some would frown upon it — bamboo tubes drilled out to appropriate sizes. I have never had a problem with bamboo, and I have found that the number of parasitised or failed cells is about equal in all three types of nesting cavity.

The ‘Pests’

(Details of the lifecycles of the following creatures are available on the internet. I will concentrate on illustrating how to keep their numbers in check for the sake of the bees.)

Mites

(Chaetodactylus osmiae). Bamboo cane on opening above. One cell is heavily infested with mites. The black specks on the left of the healthy cocoon are larval droppings, this is completely normal. Red mason bee larvae move the droppings out of the way before spinning their cocoon whereas Leafcutter bees incorporate droppings in theirs. The mites are the flesh coloured mass to the right of the yellow powder (mite droppings).

(Cacxoenus indigator) – a cleptoparasitic fly, at least in its larval form. The larvae of Cacxoenus indigator, the assassin fly. These fruit flies enter bee nesters through the tube entrance when the bee is away from her nest. When her eggs hatch, the grubs consume the pollen that was meant for the bee larvae and the bee grub starves to death. If only a few eggs are laid you just end up with a small mason bee, but a larger amount as here means no bee at all.

(Monodontomeros obscurus) – These tiny little wasps can be particularly troublesome, especially in nesters that are populated with thin walled plant stems or unprotected paper straws. Cardboard or bamboo tubes seem to protect against their attacks, at least in my experience. This is a wasp which oviposits up to ten eggs into a cocoon. The resulting larvae then eat the developing bee and overwinter as fully developed larvae within the infested cocoons. Reject any cocoons that don’t feel ‘right’. A healthy cocoon is firm to the touch, though male cocoons sometimes have dimples in them. Keep any you are not sure of in an escape proof container and see what emerges in the spring.

Safe opening of bamboo tubes

It can be a little dangerous opening bamboo tubes as I found out to my cost a few years ago. To do it safely you all you need is a simple device. This consists of a length of 75mm x 50 timber screwed to a base of 150 x 25. Two holes about 120mm deep are drilled into the 75 x 50 which are large enough for the bamboo tubes to sit in. Then if you insert a sharp knife 10mm deep across the entry end of the tube and twist it left and right the tube will open cleanly. Keep one hand on the knife handle and the other flat on top of the blade for safety. Never allow children to do this unsupervised.

Cleaning cocoons: initially, the cocoons can be cleaned by sieving them in fine horticultural sand, then you can use a soft artist brush to clean, followed with a damp cotton wool pad if required.

Cleaned cocoons, don’t forget to dry them before storage, pat them gently with some kitchen towel then leave them on another piece of kitchen towel to dry for a few minutes. Storing the cocoons when damp can lead to problems with mold which can be simply wiped off should it occur, but why create problems when a little care ensures this doesn’t happen in the first place.

Bamboo tubes should be replaced annually, though ones drilled out to 8mm can have a CJ paper liner fitted and used again. Wooden trays can be cleaned with boiling water, scrubbed with an old toothbrush and left outside to dry before going back in the nester. Tubes and slots should be at least 160mm long. 8-10mm diameter holes are good for red mason bees and 10-12mm for leafcutters. Tubes of 3-7mm may attract other types of bee too. The nesters themselves can be scalded out with boiling water and any maintenance needed doing in the autumn. Store them indoors during the winter, load them with new tubes in the spring and then you can sit back and be richly entertained by these wonderful little bees.

Refrigerate cocoons in plastic trays on a bed of damp kitchen towel. The tub of water keeps up the humidity levels to stop the bees from dehydrating. Add paper towels in the storage trays which should be dry by the way. If stored in a fridge you will need to keep the humidity levels of 60-70% so some sort of humidity indicator will be needed A temperature of around 38 – 40 degrees Fahrenheit is perfect.

Ready for the new season, the box below the nester is a release chamber where the cocoons are placed in the spring. Small nesters like this are easier to look after than the huge ones that seem to be in vogue at the moment. Small is beautiful in my opinion. The flowering currant in the background is a magnet for bees of all types when in bloom, bees at the front door, it doesn’t get any better than that!

Some may say ‘let nature take its course’, but if we put out bee nesters then surely the aim is to increase the population of bees in our gardens. That said, you can reach a bee overload situation in which case I ask friends and neighbours to host a nester in their own garden. By adopting this form of husbandry you can increase the numbers of Red mason bees year after year (given the vagaries of the weather). And if you can get a child or two interested in these lovely little creatures then surely that can only be a good thing!

Look out for another exciting installment in February, when I will give you some advice on putting your nesters outside ready for the new season, and also how to deal with Leafcutter bees. These bees overwinter as pupae so their cocoons should be left well alone until next spring.

If you would like to know more, then please get in touch with ronrock@phonecoop.coop.