The bumblebees of Bressay

Shetland’s many islands hold a special place in Scotland’s natural history. Bressay, which sits opposite Lerwick, is no exception.  Numerous seabirds and waders visit from afar, otters enjoy the voes, bonxies patrol the skies, and, as the Species on the Edge team will confirm, there are a good few bumblebees around.

Back in mid-June, the Species on the Edge team organised a day designed to encourage the public to come along and learn how to identify the bumblebee species of Shetland. There was the promise too of a look at wildflowers and the habitats important to bumblebees. 

Molly Harvey is the local Species on the Edge Community Engagement Officer and works for RSBP Scotland. She had organised the event and, as with any identification day, she spent the days beforehand with fingers-crossed, praying for fair weather. To some extent her prayers were answered, but perhaps not in the way she anticipated.

Come the morning of the event day, participants awoke to a stiff breeze. Whilst the short ferry crossing from Lerwick wouldn’t be too bad, there would be challenges in studying the bumblebees in strong winds. That’s where a good Samaritan stepped in. 

The day was ‘saved’ when a Bressay resident allowed the team to use his pollinator-friendly garden to carry out much of the surveying.  It couldn’t have worked out better. the garden has been especially curated for pollinators and was simply buzzing with bumblebees including early (bombus pratorum) and garden bumblebee (bombus hortorum). 

The garden captivated Molly to such an extent that she said, “It was totally inspiring and I would be very keen to do more about pollinator-friendly gardening here in Shetland.”

Having found a great spot there was further delight when Rory Tallack from Shetland Amenity Trust did a fantastic job of helping out with identification. He quickly had the group confidently able to tell apart the tricky to distinguish buff (bombus terrestris) and white-tailed bumblebees (bombus magnus), and along the way shared an enviable reservoir of local natural history knowledge.

And, of course, Molly was delighted that one of the target species for Species on the Edge made an appearance: “The star of the show was the very special ‘Shetland Bumblebee’, a subspecies of the Moss Carder Bee. The ‘Shetland Bee’ relies on flower-rich habitat which can include roadside verges and gardens as was demonstrated so well during our day on Bressay.”

The keenly anticipated presence of the Moss Carder Bee (bombus muscorum) was a key driver in organising the event, which was designed to engage the local community with both Species on the Edge and bumblebees in general.

It was a great day for all concerned. Plenty of inspiring company and an opportunity to explore the actions needed to help our hard-pressed bumblebees. The fun and sense of discovery certainly won‘t end with the popular June event. One of the conservation actions Species on the Edge will be taking for the ‘Shetland bumblebee’ is to recruit BeeWalkers! 

BeeWalk is a long-term national recording scheme run by Bumblebee Conservation Trust. By giving just a few hours a month between April-October, and walking a 1-mile route of the participant’s choosing, people can make a valuable contribution. All they need to do is count and identify bumblebees. This valuable data will help the Species on the Edge team and Bumblebee Conservation Trust to monitor the population status and trends of the ‘Shetland Bumblebee’. 

This will allow the Species on the Edge team see how bumblebees are responding to pressing issues such as climate change and land use change and in turn better inform and guide targeted conservation actions.  BeeWalk data is incredibly valuable and can ultimately help bring species like the ‘Shetland Bumblebee’ back from the edge before it is too late.

Tom Allan, who is the busy Project Officer for Species on the Edge in this area, is also in the process of setting up valuable roadside verge surveys. At the moment he is recruiting a group to trial the survey methodology, and his work will both help determine the status of roadside verges in Shetland and signpost opportunities to improve management for bumblebees and other pollinators.

Bressay’s 7,000 or so acres are a wildlife haven. In the air, the seas all around, and on the land, it offers home to an amazing variety of species. With Tom and Molly’s drive it looks set to offer the struggling Moss Carder bumblebee improved opportunities to thrive in the years to come, and that’s what Species on the Edge is all about.

Species on the Edge is a partnership programme of NatureScot and seven conservation charities, funded by the National Lottery Heritage Fund. The partnership consists of Amphibian and Reptile Conservation, Bat Conservation Trust, Buglife, Bumblebee Conservation Trust, Butterfly Conservation, NatureScot, Plantlife and RSPB Scotland.

Find out more:

To find out more about Species on the Edge and to keep up to date with the latest news from the programme, check out their website, Twitter, and Facebook, and sign up to their mailing list.

Key contact molly.harvey@rspb.org.uk. is happy to share a link to a recording of a bespoke training video for the bumblebee species of Species on the Edge delivered by the Bumblebee Conservation Trust.

Shetland Community Wildlife Group suggestions for pollinator friendly gardening 

Shetland Bumblebee survey 2020 and guidance sheet the Shetland Biological Records Centre are always pleased to receive ad hoc sightings of bumblebees.

People may be interested in what to do with ad hoc records of bumblebees. Firstly there is a fantastic article from the Bumblebee Conservation Trust that covers a number of different recording schemes for bumblebees on a more ad hoc basis – So you’ve seen a bee, what happens next? – Bumblebee Conservation Trust. These include A Community for Naturalists · iNaturalist and Home | iRecord. 

Furthermore sightings on Shetland are very welcome at the Shetland Biological Records Centre – there is an online recording form here Submit Records Online | Shetland Amenity Trust’.

The BeeWalk website is jam packed with resources to help you get started on your own BeeWalk Home | BeeWalk Survey Scheme. On the homepage is a link to register and also several tabs including a Resources and FAQ tab which are really helpful. If you click on the Resources tab you will find lots of documents including ‘Full guidance document’ which is a step-by-step guide to registering as a BeeWalker and setting up and performing your BeeWalk.

There is also a Bumblebee Conservation Trust youtube channel which contains BeeWalk tutorials as well as videos on identification and survey skills. Bumblebee ID & BeeWalk survey training – YouTube

PlantNet is a fantastic app that is particularly well-rated and iNaturalist also have an app that can be used for plant ID and also to submit and share your findings. The following link provides information on how to identify plants on your iPhone -> Look up what’s in a photo with your iPhone or iPad – Apple Support (UK).

With sincere thanks to Molly Harvey, Tom Allan and Eilidh Ross for all their help in compiling this blog.

Flavour of the month

By Athayde Tonhasca

Many things can be ‘plain vanilla’, but vanilla is not one of them. This spice comprises a complex mixture of vanillin and other organic compounds that produce its distinctive flavour and aroma. The main source of vanilla, the flat-leaved vanilla orchid (Vanilla planifolia), is native to Central and South America but grown commercially in tropical areas around the world; Madagascar is by far the largest producer, followed by Indonesia. 

A flat-leaved vanilla orchid © Malcolm Manners, Wikimedia Commons.

Vanillin is found in the orchid’s ‘beans’ (botanically speaking, its fruits), and it’s not easy to get. The vanilla orchid grows as a vine that can extend for 20 to 50 metres, so it needs supporting structures to spread out. In its native range, the vanilla flower is pollinated by bees; elsewhere, it is hand-pollinated (you can watch how this is done). The operation has to be quick because a flower remains receptive for about 24 hours. If not pollinated, it wilts and falls to the ground. The beans take six to nine months to mature; when ready, they are hand-picked, dipped in hot water and dried for up to a month. So it’s not surprising that such a labour-intensive crop doesn’t come cheap: as spices go, only saffron costs more by unit of weight.

So how come your run-of-the-mill vanilla ice-cream or cake is not particularly dear? Because about 99% of all vanilla products (food, beverages, cosmetics and pharmaceuticals) are flavoured with synthetic vanillin, which can be obtained from wood pulp, clove oil, coal tar and other petrochemicals, and it’s about 20 times cheaper than natural vanilla. Chefs, bakers and food buffs debate the organoleptic differences between natural and synthetic vanilla. Whatever their verdict, the food industry is under growing pressure to reduce artificial flavours from their products, so production of natural vanilla remains strong and tends to increase.

The real deal (vanilla fruits), and ‘plain vanilla’ (artificial vanilla flavour) © Bouba and Maik Führmann, respectively. Wikimedia Commons.

The growing value of natural vanilla is promising to small farmers in Madagascar and other developing countries, but there are clouds on the horizon. Almost all natural vanilla comes from a single species cultivated as a monoculture in a few areas around the globe, and all plants are obtained by cloning (cuttings). These distribution and propagation patterns promote genetic uniformity, which is a risk to vanilla production. A simplified and impoverished genetic base makes the crop vulnerable to diseases and pests, which are similar threats to those hanging over the genetically homogeneous bananas available to European and American consumers.

One way to reduce these risks is in-situ conservation, that is, the protection of flat-leaved vanilla orchids in their places of origin. These areas are natural gene banks, potential sources of genetic material that could be incorporated into crops to help them adjust to new environmental stresses. And here, bees may have a lot to contribute.

In the wild, flat-leaved vanilla orchids grow in isolation deep inside mature forests, climbing from one tree to another. When plants reach a certain size, they produce only a handful of flowers. A pollinator needs special skills to locate a flower in the chaotic, crowded environment of a tropical jungle. This is a job for orchid or euglossine bees (tribe Euglossini). Females gather pollen and nectar like any ordinary bee, but males spend a great deal of their time collecting volatile compounds, primarily from orchids; they can fly for dozens of kilometres in pursuit of the right scent. Males store a variety of these chemicals, and the resulting aromatic bouquet advertises their prowess to females. Many orchids take advantage of this perfume obsession: they are especially adapted to transferring pollinia (pollen packets) to the bodies of visiting male orchid bees.

L: an orchid normally hidden in the forest canopy was brought down and exposed by a tree fall © Tatiana Gerus; R: a male Euglossa analis © The Packer Lab, Wikimedia Commons.

Orchid bees are the main, or possibly the only, pollinators of the flat-leaved vanilla orchid, although we have only sketchy details about specific species. These bees play another role in the orchid’s life, one that has been recognised only recently: as seed dispersers.

Orchid bees collecting scents from mature fruits of flat-leaved vanilla orchids. A: Euglossa sp. B: Eulaema sp. C: Exaerete sp. © M.A. Lozano Rodríguez (Rodríguez et al., 2022).

Seed dispersal is as important as pollination. By having its seeds spread out over large distances, a plant does not have to compete with its seedlings. Dispersed offspring also has a better chance of escaping predators, diseases or environmental misadventures that may befall the parent plant. Herbivores play a big part in dispersal: the seeds in the fruits they eat will end up in a steamy, fertilised pile somewhere. However, mammals and birds are not tempted by most orchids because their fruits are not particularly nutritious. It makes no difference for most orchids; their seeds are easily uplifted and dispersed by the wind: for some species, 3 million seeds weigh as little as 1 g.

But things are different for Vanilla spp. and a few other orchid genera: they produce fleshy fruit whose seeds are protected by a hardened coat and not easily carried by the wind. These characteristics suggest zoochory (seed dispersal by animals), and indeed rodents and marsupials eat the fruits of flat-leaved vanilla orchids, later passing the seeds. Karremans et al. (2023) discovered that some male orchid bees and female stingless bees (tribe Meliponini) join the feast: they take seeds away when the fruits split open naturally. So the flat-leaved vanilla orchid is likely to be part of a select group of plants with mellitochorous seeds, i.e., dispersed by bees. Mellitochory is not common, but this could reflect our lack of knowledge more than rarity of the phenomenon. Most recorded cases involve seeds hitching a ride when stingless bees collect resin or other nest-building material. Later these seeds fall off or are chucked out of the bees’ nests, germinating on the ground. 

(a) A Trigona carbonaria stingless bee taking resin from a cadaghi (Corymbia torelliana) fruit in Australia. Note the resin in mandibles and corbiculae (scale bar = 1.6 mm). (c) T. carbonaria carrying resin and seed of C. torelliana (scale bar = 1.5 mm). Photographs by Robert B. Luttrell © Wallace et al., 2007.

To summarise: there’s a global craving for natural vanilla, which is extracted mostly from one species of orchid whose populations are vulnerable to genetic homogeneity. Protecting native orchid habitats would allow bees to give a hand by pollinating flowers and dispersing their seeds, thus helping safeguard commercial flat-leaved vanilla against future vicissitudes. This intricate tale is anything but plain vanilla. 

The orchid bee Eulaema polychroma is one of the species likely to pay a visit to flat-leaved vanilla orchids © Insects Unlocked, Wikimedia Commons.

Where good news is standard

Don’t you just love it when you open up an email and feel a warm glow? That sensation happened to me a few days ago when Susan from the FARE Lochend Community Allotment contacted me with an update from Easterhouse containing a batch of fantastic photographs.

Back in April 2021 local residents in Easterhouse set to work on getting an area of allotments up and running again. To say they succeeded is to put it mildly. The group they turned to was FARE Scotland, a grassroots charity working to improve people’s aspirations, improve their life chances, and tackle poverty and its symptoms.

Today they not only sow, grow and harvest their own vegetables, they embrace the local community. Just listing the number of groups who make use of the site is heart-warming – Fareplay Nursery, St Clare’s Day Nursery, Buchlyvie Nursery, Lochview Nursery, Westerhouse Family Learning Centre, Oakwood Primary, St Benedict’s Primary, Lochend Community High School, Busy Bees Childminders, the Daffodil Club … the list goes on. To say Lochend is a popular site is to put it mildly.

It’s not just the pollinator team at NatureScot and Keep Scotland Beautiful staff that are full of admiration for the work Susan delivers. Others think so too.

Angela from the Royal Horticultural Society visits regularly to promote wellbeing by delivering free workshops and a ‘Grow To Eat’ wellbeing programme. Children, families and volunteers in the area enjoy the sensory garden, a rock garden, a wildflower garden, a quiet peaceful sanctuary, bird watching area, mud kitchen and much more. It’s a catalogue of success after success.

There is a great deal of talk these days about encouraging the private sector to get involved in nature-related activities and support. The folks at Lochend are on the ball here too. They have worked closely with Jewson, B&Q in Parkhead, Scotbark, Assist Glasgow, MKM building, Wickes, Johnstone’s Paints, Alba Engineering, and are immensely grateful for a range of donated materials and plants. Recently volunteers from Hymans, Robertson & Morgan Stanley helped out with maintaining the rockery and creating an extension to the group’s woodland area.

Visit today and you will find that everywhere is bursting with colour and life. The NatureScot community pollinator seed packs have been put to good use and the reward is a runway of nectar through the garden. The rewards for pollinators are superb and visitors thoroughly enjoy seeing the increased numbers of butterflies, moths, bees & dragonflies.

On top of all this the children at the FAREPLAY Nursery rescued a hedgehog from the street, took it to their hedgehog house on the allotment and felt pretty pleased about their rescue. Little wonder they received a 5-star award from the Royal Horticultural Society and scooped a further award from Keep Scotland Beautiful for engaging children and young people.

FARE Scotland is a voluntary organisation working together with communities throughout Central Scotland, on the evidence of Susan’s email they have a lot to be proud of.  In an era when good news is not always easy to come by, the folks at Easterhouse fair brightened my day with their fantastic update.

Find out more

Visit the FARE Scotland website

FARE Lochend Community Allotment

Keep Scotland Beautiful – It’s Your Neighbourhood

All images copyright and permission of Susan Wilson of FARE Scotland

Protecting our pollinators

Professor Graham Stone is Professor of Ecology in the School of Biological Sciences at the University of Edinburgh. His work, with Damien Hicks and others, has led to key changes in biodiversity strategies and impact across Edinburgh and beyond. We are grateful to University of Edinburgh for permission to reproduce the article below (written by Charlotte Stapley) which looks at Professor Stone’s Urban Pollinators project.

​​​​​​​Found across almost every continent, bees have been pollinating plants for millions of years, but their numbers are dwindling. University of Edinburgh research is working to halt their decline.

Bees, and pollinators in general, are vital for our world. The ecosystem service of pollination is essential for the continuation of natural ecosystems, and central to the productivity of many human crops. However, populations of many bees and other pollinators are shrinking.

Professor Graham Stone is Professor of Ecology in the School of Biological Sciences at the University of Edinburgh. His work, with Damien Hicks and others, has led to key changes in biodiversity strategies and impact across Edinburgh and beyond. 

Understanding the significance of pollinators, and working to identify solutions to protect and support them, is vital to the future health of the planet. 

A sharp decline

Recent years have seen a steep decrease in the number of pollinators found across the globe. New diseases, urbanisation and an increase in farming and pesticide use have all contributed to the drop. 

Dwindling numbers of pollinating insects can lead to huge sustainability challenges, including threats to human food production and increasing risks that fragile ecosystems will collapse. Beyond that, the UK National Ecosystem Assessment estimated the production value of insect pollination in the UK to be £500,000,000 per annum based on the economic value of the crops produced. 

A collaborative approach

Professor Stone was a founding member of the Urban Pollinators: ecology and conservation project – a collaboration between academics in Edinburgh, Bristol, Leeds and Reading to understand and improve the health, abundance and diversity of pollinating insects in each city and the surrounding area. The project was the first of its kind in the world to look across a range of urban areas in the UK and share results.

The Urban Pollinators team

The Urban Pollinators project set out to investigate which habitats are home to which pollinating insects, focusing on cities, farmland and nature reserves. It then went on to compare different urban habitats such as parks, allotments, graveyards and industrial sites, to identify those that provide the most food for pollinators (flowers, and the nectar and pollen they contain) and support the biggest pollinator populations.

Finally, the work looked to how these spaces can be improved to encourage biodiversity in cities and reverse some of the negative effects urbanisation has had on pollinator populations.

Local solutions

Many solutions proposed as a result of the study are easily achievable, and have the potential to undo years of damage. One simple approach, quantified in the study, is to simply allow the populations of common urban flowers such as dandelions to grow. A second is to convert parts of some city parks into wildflower meadows – which are nectar and pollen rich – essentially, pollinator restaurants.

The findings of the research coincided with Professor Stone’s involvement in the Edinburgh Living Landscape initiative (ELL), a collaboration between the City of Edinburgh Council, Royal Botanic Garden Edinburgh, Edinburgh and Lothian Greenspace Trust and the University, that is managed by the Scottish Wildlife Trust. The project works to include nature in as many urban neighbourhoods as possible across the city.

The research also had a huge impact on local policy and strategy. The Parks, Greenspace and Cemeteries team within Edinburgh City Council implemented several successful biodiversity enhancing projects due to Professor Stone’s work.

As a direct result of this research, more investment in the creation and maintenance of wildflower meadows led to one tenth of Edinburgh’s parkland being turned into wildflower meadows between 2014 to 2016, 78 of which were part of the Edinburgh Shoreline Projects, another part of the ELL initiative.

One of the wildflower meadows at Crammond

Policy changes included banning herbicides in parks and reducing mowing from fortnightly to once a season. This has the double benefit of increasing the nectar and pollen available for pollinators from wildflowers such as dandelions, while at the same time saving £200,000 in maintenance costs per year.

It also led to the inclusion of beekeeping in the allotment policy, encouraging bees to be kept in areas with rich potential for biodiversity.

Informing policy

It’s not just the local area that has benefitted from this work. In 2017, as a part of the Biodiversity Route Map, the Scottish Government launched a Pollinator Strategy, which has been influenced by Professor Stone’s research.  

His work was also referenced in the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services’ (IPBES) 2016 report on Pollinators, Pollution and Food Production, which was formally endorsed by theUnited Nations Environment Program for the Convention on Biological Diversity. As a result, it has influenced strategies in numerous countries including the UK, France, the Netherlands, and Brazil.

In 2020 Professor Stone’s research was also used in two European commission reviews, and detailed information on implementing best practice for policy makers and land use practitioners on how to adapt urban areas to effectively support pollinators, as well as ways to reverse pollinator decline.

Other Scottish councils are now beginning to implement their own approaches to urban greenspace management. The Scottish Borders Council and Dundee Council have both launched their own biodiversity plans using information from Stone’s work.

Seeds of change

Professor Stone has also worked closely with Scotia Seeds, who specialise in providing seeds of native Scottish wildflower plants, to create a specific urban pollinator seed mix. Taking into account the different growing seasons of plants, has resulted in the Urban Pollinator Seed Mix, a combination that provides nectar and pollen for as long as possible through the year.

Another of the Crammond wildflower meadows

The Urban Pollinator Seed Mix contains 22 wildflower and 6 grass species, including plants that flower throughout the spring and summer and enough grasses to provide substantial food throughout the season. The seed mix is now sold throughout Scotland to local authorities, community groups and hundreds of gardeners – alongside a coastal seed mix too.

Broader benefits 

The benefit of working with wildflower meadows is that they have well documented positive effects for human health and wellbeing, as well as providing food and drink to bees, butterflies, and other pollinators. And even after the flowers have passed, the meadows provide a banquet for seed-eating birds such as gold finches and green finches.

Professor Stone is proud of his work, but he’s keen to stress there’s more to be done: “Of all the projects I’ve been involved in, the Urban Pollinators Project has been the easiest to explain and justify to non-scientists. This is probably because it is pretty clear that if we improve the world for pollinators, we improve it for many other species – including humans! The feedback I get from people when we are out working on the meadows is the most positive and life-affirming I have ever had, and it’s great to be doing something that genuinely makes people happy.

“In the longer term I would like to see the principles we have developed applied to larger areas across cities and towns in the UK and elsewhere – starting with University of Edinburgh green spaces! It is not always easy to see how we can reduce or eliminate negative impacts of human activity, but improving urban habitats is a really good example of where, with a little investment and imagination, we can make things much better.”

Acknowledgement: This article and the images within first appeared on the University of Edinburgh website. The article was written by Charlotte Stapley, Publications Officer in their Communications and Marketing team.

All image courtesy and copyright of Graham Stone.

Foggie-toddlers and confusing history lessons

Delving into The Scotsman archives can be a pleasant way to spend an evening. You never know what you will stumble across, and it is often surprising how history appears to repeat itself. That proved the case when I typed ‘bumblebee’ into the search box. 

Bumblebee identification classes are very popular today, with good reason.  As I trawled the newspaper’s archives it was soon clear the challenge of correctly identifying bumblebees is nothing new. 

My search had carried me back almost 100 years ago. A regular running feature in the Saturday edition was ‘Nature Notes’. In July 1924 the author had asked, under a sub-heading ‘The Humble-Bee’, if any readers had noticed how few ‘humble-bees’ are to be seen this summer?

“At this time of year,” they went on to note, “the fields and highways are usually alive with the hum of what we call in Scotland ‘the bumble-bee, but this year ‘bumbees’ seem scarce. The long, cold spring, perhaps, explains the situation – many of the queens would succumb for want of food, blossom of all kinds being about a month later than usual. Whether this toll in the bumble-bee species will affect the fertilisation of plant life throughout the year is a question for experts. No insect contributes in greater proportion to the fertilisation of plants than ‘wild bees’.”

It’s an interesting snippet on many levels.  The use of the terms Humble-Bee, bumble-bee, and bumbee, in one short article is quite striking.

A few days later The Scotsman carried a response from Philipstoun near Linlithgow. The writer went on to confirm that they too had scarcely seen any ‘bumble-bees’ but mentioned that on the cotoneaster growing on the walls of their manse, were large numbers of ‘wild bees’ visiting the abundant small pink flowers.  

The description of the species was “being not so large as the well-known ‘bumble-bee’”.  It was apparently “black with a bright yellow band on the segment behind the head, and the hindquarters had a band of reddish tinge dominating the yellow, some of the bees had a yellow band on the ‘posterior segment’ of the body”. 

We will never be sure what the writer saw, but it seems likely from the description that they did indeed have bumble-bees (possibly the early bumblebee) but not the relatively common buff-tailed or white-tailed species.

It’s a subject that crops up at bumblebee conferences to this day – just how tricky it can be for non-specialists to be 100% sure of bumblebee identification. Some things it seems never change, and at our most recent conference it was seen as perhaps the biggest single challenge facing the citizen scientist who wishes to submit records and engage in monitoring. So much so that in some instances records are invited which are submitted merely as ‘general’ rather than ‘species specific’ bumblebee records.

Back to the archives, and five years later, in 1929, bumblebees were again capturing the imagination of The Scotsman readership.

“Humble-Bees or Bumble-Bees” was the title given to a letter from A Robertson in March 1929. They challenged an earlier correspondent who had stated that ‘there were three varieties of bumbees” in Scotland. Robertson went on to point out that ‘actually there are 17 species of Bumble-bee in the British Island, and of these bumblebees – known as bumbees in rural Scotland – more than half were found in Scotland.” However, conceded, “to the untutored in the lore of bumble-bee life history, many of the species will be indistinguishable from each other. The colour markings bear considerable resemblance to one another.” 

The carder bees were a point in case.

Picking out Bombus muscorum, they noted that the earlier article “referred to them as the ‘Foggie-toddler’ – the moss bee – so similar to B. agrorum (Bombus pascuorum today) – the field bee – that only experts can single these out. And so (too) in the case of the yellow and white banded bumblebees.” 

But wait, there is more.

One reader recalled that when out fishing as a boy the river banks had “fairly swarmed with wild bee’s bykes”. 

Today we more readily associate the word ‘bykes’ with wasps nests, but back then it was clear that the reader was spotting carder nests in grass mounds which the local gamekeeper called ‘riggins’. The writer apologetically stated that alas he ‘harried’ many of these nests. This appears to have been moss carder bumblebee nests, as the reader differentiates between ‘bumblebees’ nesting in holes in the ground, “whereas the wild bees’ nests were in the grass or moss tufts.”  

Old names, new names, different names – it matters little, it seems that identification has been a constant challenge.

Notes

You can access The Scotsman archive as a card holder at the National Library of Scotland. 

Today there are 24 resident species of bumblebee in Britain (see https://www.bumblebeeconservation.org/about-bumblebees/ 20 of which occur in Scotland. Since 1929, Bombus cullumanus and Bombus subterraneus (neither present in Scotland) have gone extinct, but the latter has been reintroduced, and we’ve recently gained Bombus hypnorum – which is spreading in Scotland. 

Together, for better or worse

By Athayde Tonhasca

In 1844, Captain John C. Frémont of the US Army Corps of Engineers, later a US Senator and Governor, was crossing the Mojave Desert when he came across a Joshua tree (Yucca brevifolia), hitherto unknown to white settlers. In his report, the captain offered a harsh appraisal of his findings: “Associated with the idea of barren sands, their stiff and ungraceful form makes them to the traveler the most repulsive tree in the vegetable kingdom”. But Frémont was moderate when compared to Joseph Smeaton Chase, British-American author of California Desert Trails (1919): “One can scarcely find a term of ugliness that is not apt for this plant. A misshapen pirate with belt boots hands and teeth stuck full of daggers is as near as I can come to a human analogy. The wood is a harsh, rasping fibre; knife blades long hard and keen fill the place of leaves; the flower is greenish white and ill smelling; and the fruit a cluster of nubbly pods, bitter and useless. A landscape filled with Joshua trees has a nightmare effect even in broad daylight: at the witching hour it can be almost infernal”.

Joshua trees © Joshua Tree National Park, Wikimedia Commons.

Frémont’s and Smeaton Chase’s unfavourable aesthetic appraisals are not widely shared: many gardeners and landscapers like the peculiar shapes and looks of yuccas or palm lilies (Yucca spp.), so several species are grown around the world as ornamentals. Most of the 40 or so known species grow as shrubs or trees with spiky, sword-shaped leaves; they produce large clusters (panicles) of bell-shaped, creamy-white flowers on stalks rising from the centre of the plant. Yuccas are symbolic of their places of origin, the great open spaces of the American and Mexican deserts. They definitely appealed to German-American physician and botanist George Engelmann (1809-1884), who became the world’s authority on the genus.

Yucca forest in San Luis Potosi, Mexico © Tomas Castelazo , and a cultivated Adam’s needle (Y. gloriosa) © Magnus Manske, Wikimedia Commons.

From his observations, Engelmann suspected that yucca flowers did not self-fertilize because of their morphology. Their anthers are orientated away and at a different level from the stigma, making it difficult for pollen grains to move from the former to the latter. To make the task even more challenging, yucca pollen is viscous, forming dollops not easily broken apart. Because yuccas tend to bloom at night, Engelmann reasoned that moths must be involved in pollen transport. In 1872, he collected some small, non-descript, whitish moths seen gallivanting around yucca flowers and gave them to British-American entomologist Charles Riley (1843-1895). Geographical serendipity helped Engelmann’s generous act of scientific collaboration: both men lived in St. Louis (Missouri). 

Flower of a Spanish bayonet (Y. aloifolia). From The Yucca Moth and Yucca Pollination, by C.V. Riley, 1892. Wikimedia Commons.

Riley took up the challenge, and his discoveries about the role of those obscure white moths in yuccas reproduction were nothing short of spectacular; in a letter to Joseph Hooker in 1874, Darwin described Riley’s findings as ‘the most wonderful case of fertilisation ever published’.

Riley identified and named the yucca moth as Tegeticula yuccasella, from the family Prodoxidae (subsequently, several species from the genera Tegeticula and Parategeticula have been recognised as yucca moths; they are difficult to tell apart, but all more or less follow the T. yuccasella pattern). After mating on a flower of soapweed yucca (Y. glauca) or a related species, the female scrapes pollen from the anthers with a pair of specialised, spiky tentacles: these structures, which are found in no other group of insects, replace the long ‘tongue’ (proboscis) characteristic of most moths and butterflies. Without a tongue, the yucca moth can’t feed. But that’s not a problem, since the moth’s life is very short. The female uses her tentacles and sometimes forelegs to compress the glutinous mass into a ball containing up to 10,000 pollen grains, and holds it under her ‘chin’.

A female T. yuccasella carrying yucca pollen in her tentacles, which are absent in males © Jim Petranka, North Carolina Biodiversity Project.

Done with pollen gathering, the moth takes flight in search of another flowering yucca – not an easy job, as the pollen load may weigh up to 10% of her body mass. On arrival, she walks to the base of a flower to find its ovary, opens a small hole in it and lays her eggs inside. Things then become truly interesting. By using the tips of her tentacles, the moth removes a small portion of her pollen load, walks to a stigma and places the pollen on it. You can watch these steps unfolding.

Before leaving the flower, the moth marks it with a pheromone to prompt latecomers to look somewhere else for their own egg-laying. The eggs hatch and the larvae feed on some of the developing seeds. At the end of their development, the larvae leave the fruits resulting from the seeds, fall to the ground, bury themselves in the soil, build their cocoons, and start a new cycle in the following spring. 

L: a female T. yuccasella gathering pollen, by C.V. Riley, 1892. R: A Tegeticula sp. moth depositing pollen on a yucca stigma © Sherwin Carlquist, Wikimedia Commons.
 

The yucca moth’s actions deserve pause for thought. When we say that an insect has pollinated a flower, we may assume it’s a deliberate act: almost invariably, that’s not the case. A pollinator would eat or take all pollen back to its nest if it could. Pollination happens by accident, when the flower visitor drops off a few pollen grains in the right spot, or has pollen brushed off by touching some part of the flower. Bees may carry away 95 to 99% of all pollen gathered, leaving the remainder – unintentionally – for pollination. But it is tit for tat in these liaisons: plants have developed adaptations to minimise pollen harvesting, such as inconspicuous anthers, narrow floral tubes, difficult flower structures, or progressive pollen release to force pollinators to make repeated visits. Some plants like orchids also cheat by attracting pollinators with scent but not giving any nectar or pollen in return. Rather than collaborating, then, insects and flowers are taking advantage of each other. Granted, this mutual exploitation has been fine-tuned by natural selection to avoid disastrous imbalances: overly rapacious insects and pollen-stingy plants would collapse their dealings. But unusually for these mutualistic relationships, the yucca moth deliberately pollinates yucca flowers. This process guarantees the yucca a faithful and efficient pollinator for the price of a few seeds, while the moth is compensated for its troubles with a safe and nutritious site for its offspring. 

Riley, an early evolutionist, understood immediately the implications of this mutual back-scratching. “These peculiarities are (…) mutually and reciprocally beneficial, so that the plant and the animal are each influenced and modified by the other, and the same laws which produced the beneficial specialization of parts would maintain them by the elimination of all forms tending to depart from them” (Riley, 1873. Transactions of the Academy of Science of Saint Louis 3: 55-64). Darwinian references didn’t go well with evolution-hesitant Engelmann, who mumbled that “such theories would lead us astray” – see Sheppard & Oliver (2004) for a detailed account of Riley and Engelmann’s professional relationship. 

It’s not surprising, then, that Riley’s findings thrilled Darwin, who briefly mentioned reciprocally beneficial flower and pollinator traits in the Origin (1859), and developed the idea – which he called co-adaptation – in his book on orchid pollination (1862). Darwin famously predicted that a Madagascan orchid with a very long spur (a tubular projection where nectar is stored), known today as the Darwin orchid (Angraecum sesquipedale), had co-adapted with a then unknown hawkmoth with an exceptionally long tongue. And his prediction turned out to be right. 

The concept of co-adaptation was renamed ‘coevolution’ by Ehrlich & Raven (1964) in their celebrated paper on butterflies and their host plants, and it is today understood as a reciprocal evolutionary change resulting from the interactions between species. The extent of coevolution as a force behind pollination has been a matter of debate, since there isn’t much one-to-one specialization involved: insects usually pollinate many flowers, and plants in general are pollinated by more than one flower visitor. Moreover, pollination is mostly a passive by-product of a visitation for the purposes of gathering pollen, nectar, oils, or other flower resources; see for example Johnson & Anderson (2010) for a discussion. But in the case of yuccas and their moths, it would be difficult to refute coevolution; plants and insects couldn’t survive without the intricate idiosyncrasies that favour each other. 

Darwin had a reason to be pleased to learn about the contrivances of some strange plants and their cryptic pollinators from the vast North American deserts. And if Captain Frémont and Smeaton Chase knew about the delicate balance between the Joshua tree and yucca moths, they may have been bestowed a more sympathetic judgement. 

Yucca moths on a yucca flower. Photo by Alan Cressler, U.S. Department of Agriculture.