23 July 2019

by Katy Malone, Bumblebee Conservation Trust Conservation Officer for Scotland

Being a fully paid-up member of the bumblebee fan club, no-one will be surprised to learn that when I finally got offered an allotment in my village three years ago, I set out to make it as bee-friendly as possible. After all, growing veg and attracting crop pollinators with nectar and pollen-rich flowers – well, it’s just a no-brainer.

That said, my fellow allotmenteers and I each have our own distinctive style of growing, which probably reflect our personalities. The gentleman with the plot next door to mine grows very traditionally in very neat, die-straight rows. Potatoes are earthed up in immaculate V-shaped furrows, all the same height and distance apart. He plots out carrots in a millimetre-accurate grid. Every scratch of ground is used for crops of some sort. One a sunny day in May, he spotted the packets of bulbs I brought for planting in the pre-prepared ground and was intrigued.

“Oh, what’s that you’ve got?”

“Gladioli blubs – a lovely mixture of…”

…but he had already turned away in pretend disgust. Of course, I was letting the side down! We joked about it, but I know he’d really prefer me to be grow swedes rather than ‘wasting’ the available space with flowers. He still borrows my rake when I’m not around though.

The plot opposite has lots of flowers as well as crops, in higgledy piggledy rows. She’s a child minder, and her young charges often come down to help her in the allotment.  She grows lovely sweet peas, lilies and cosmos, the veg and the flowers being mostly separate from each other.

My own plot is something of a potager style, with blocks of edible crops interspersed with colourful flowers which attract pollinating insects like bumblebees (of course!) as well as honeybees, wasps, and hoverflies. I get a great sense of satisfaction by growing from seed, and this year almost all my crops are grown this way (except potatoes from sets, and garlic which I grew from cloves saved from last year’s crop).

Cornflowers, self-sown foxgloves and cosmos all attract a variety of beneficial insects. The cornflowers are part of my plan to grow flowers for cutting, but if an insect happens to be feeding on the freshly emerged flower, I leave it alone. I would feel so guilty for depriving any bee of its lunch! If a few crops start bolting, and I don’t need the space immediately, I’ll let them flower. The hoverflies are particularly keen on the towering blooms of Swiss chard, which bloom profusely before flopping over in the wind and need to be propped up or cut back.

Some ‘weeds’ are particularly beneficial and I let them grow amongst my veggies, as long as they don’t start to take over. Red dead-nettle is a favourite with long-tongued bumblebees, which in turn are brilliant pollinators of my runners and broad beans. The shorter-tongued honeybees and hoverflies can’t reach the nectar in these long-flowered crops, and so cannot pollinate them. Encouraging longer tongued species like garden bumblebee and common carder bumblebees by providing a greater diversity of long flowers is good for a quality crop set. I know there are modern F1 crop varieties which are self-setting, but I prefer to grow open-pollinated heritage varieties. For me, it goes against the grain to do anything else.

It would be great to think that all this results in better pollination of my crops – and really, I have no first-hand evidence that supports that. However, a research paper1 published in Nature earlier this year revealed that allotment sites are very valuable spaces in an urban context. The researchers showed that residential gardens and allotments in four different cities across the UK were major hotspots for pollinators, highlighting the value of these places for supporting vital pollinator conservation. In his regular summary of recent science papers ‘Bombus Review’ (Bombus review – Spring 2019) my colleague Darryl Cox wrote of this paper:

“The authors end their report with some really useful and practical suggestions for maximising the pollinator potential of urban areas. They suggest that town planners try to add more allotments to towns and cities as even a small area increase could make a big impact on the robustness of plant-pollinator communities.”

Watching bees work those multi-coloured cornflowers, benefitting from the abundant nectar and pollen from the red dead-nettle and enjoying the late boost of forage from the gladioli and self-sown foxgloves gives me satisfaction beyond words. When I’m enjoying freshly-podded broad beans, lightly steamed with butter and parsley and a squeeze of lemon, I am even more glad to be supporting the bees in my little corner of paradise.

1. A systems approach reveals urban pollinator hotspots and conservation opportunities. Baldock, KCR et al, Nature Ecology & Evolution volume 3, pages 363–373 (2019)

Managing your bee hotel

Periodic maintenance and cleaning will result in a more successful nest box and a healthier population of bees in your garden. With no cleaning, fungi, debris and parasites tend to build up which can be damaging to the bees.

• Bring your nest box into an unheated shed or garage during the autumn and winter to protect it from damp and wet weather. If you don’t have either then a porch or any covered area will do. It is damp not cold that destroys larvae. Not only will this protect the larvae and adult bees waiting to emerge in the spring but it will mean that your nest box will last longer. You can place the box outdoors in the spring, from March onwards.
• If you notice birds predating your nest box or removing nest tubes (woodpeckers and tits often do this) then you can place a piece of mesh or chicken wire across the front. This does not appear to deter the bees.
• If your nest box is built of stacked & routed wooden sheets or you use paper nest tube liners you can clean it out in winter, remove the cocoons (image left) and store them until spring.
• At least every couple of years replace all of the tubes and blocks in the nest box with fresh ones. In spring leave the old tubes in an upturned box or bucket on the ground with a hole at the top (bees naturally orientate towards light) so that the previous year’s bees can emerge but so that they won’t reoccupy the old tubes.

For further information on all of the above Marc Carlton of ‘The Pollinator Garden’ has produced an excellent guide to ‘Making and Managing a Bee Hotel’. A pdf. version can be downloaded from www.foxleas.com

George Pilkington also has a fantastic website and blog ‘Nuturing Nature’ www.nurturing-nature.co.uk which has a wealth of information on managing bee houses.

For photos and more information about the bees and wasps that are attracted to nest boxes the website of The Bees, Wasps and Ants Recording Society ‘BWARS’ is very helpful  www.bwars.com

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