On a wing and a prayer: butterflies in action

By Athayde Tonhasca

The peacock flower (aka red bird of paradise or pride of Barbados, Caesalpinia pulcherrima), originally from tropical regions, and the flame azalea (Rhododendron calendulaceum), an American native, are favourites among British gardeners and landscapers. These plants’ species epithets explain their popularity: pulcherrima, Latin for ‘prettiest’, and calendulaceum, ‘of the colour of calendula’, refer to their flamboyant inflorescences of yellow, red, and orange tones. 

Peacock flower (L) and flame azalea © Rennboot (L) and Daderot, Wikipedia Creative Commons

These plants are not related, but if you examine their flowers, you will notice they share one feature: their anthers (male parts) and stigma (female parts) are elongated and at a considerable distance from one another. Botanists call this spatial separation between male and female structures herkogamy. This feature, just like dichogamy (when male and female reproductive organs mature at different times), reduce the interactions between pollen and stigma of the same plant, therefore reducing the chances of inbreeding. 

Peacock (L) and flame azalea flowers © BARAKAT2011 (L) and Arx Fortis, Wikipedia Creative Commons

Herkogamy would be a headache for plants relying on bees or flies for pollination. Considering the size of the flowers and the way their reproductive structures are spread out, it’s unlikely that these insects would come into contact with both anthers and stigma. The peacock flower and the flame azalea need pollinators capable of handling these awkward morphological quirks. They need butterflies.

Butterflies are familiar, prevalent and showy flower visitors, but visitation alone does not make a pollinator. Pollination requires the transport of a sufficient number of viable pollen grains to the right stigma at the right time. And, generally speaking, butterflies are not good at it. They are not particularly ‘hairy’ and lack specialized pollen-collecting structures. Most species don’t feed on pollen, and are quite skilful in avoiding it by slurping nectar while perched on their long legs. So psychophily (pollination by butterflies) has been demonstrated here and there, such as for some orchids and in the cotton fields of the American Gulf Coast. But cases are relatively rare, and mostly in the tropics. Many an uncharitable ecologist has categorised butterflies as ‘parasitic nectar thieves’ because they deplete flowers of a metabolically expensive product without contributing to their pollination.

To the peacock flower and flame azalea, butterflies are anything but parasitic. They deal with structures that stick out like bristles on an old brush by fluttering over the flower, inspecting it before landing to sip its nectar. By doing so, they touch the anthers, and pollen grains get attached to the ventral surface of their wings. When they repeat these manoeuvres on another plant, some of the pollen will fall on or be brushed off by the pistils, enabling cross-pollination.

A blue Mormon butterfly (Papilio polymnestor) nectaring on a peacock flower in India © Project Noah

Size is important in this pollen-gathering mechanism, as reaching both anthers and stigma requires wings with large areas. So big swallowtails (family Papilionidae) are the main pollinators of these herkogamic flowers. And the more they flap their wings, the better. In the case of the flame azalea in its native Appalachian Mountains, the great spangled fritillary (Speyeria cybele) gathers pollen in its wings, but not nearly as much as the eastern tiger swallowtail (Papilio glaucus). The former stays still once it lands on the flower, while the latter keeps fanning its wings, thus increasing the chance of contact with anther and stigma. The outcome of wing pollination has been measured experimentally: when butterflies were excluded from flame azaleas, their fruit set was almost nil. 

The great spangled fritillary (L) is a flame azalea’s pollinator, but the eastern tiger swallowtail is even better © Mdf (L) and Ryan Hodnett, Wikipedia Creative Commons

An unusual flower shape may be a hint of adaptation to wing pollination. Another garden favourite, the South African blood lily – also aptly known as ball lily, fireball lily, and powderpuff lily (Scadoxus multiflorus) – seems to have been designed to make life difficult for pollinators. But butterflies are not deterred by its porcupine look. They flap their wings and get their nectar, picking up some pollen while they’re at it. 

A citrus swallowtail (Papilio demodocus) (L) and a mocker swallowtail (P. dardanus) nectaring on blood lilies © HC Butler (L) and Steven D. Johnson. Source: Butler, H.C. 2020. Scadoxus multiflorus and its butterfly pollinators. PlantLife SA

These herkogamic species do their bit to facilitate butterfly pollination. Their yellow/red colours are particularly attractive to these insects, so flowers are easily located. And their pollen is sticky and relatively flattened, so it adheres to the scales of a butterfly wing.

Blood lily pollen attached to the wing of a butterfly © Butler, H.C. 2020. Scadoxus multiflorus and its butterfly pollinators. PlantLife SA

In his ‘butterfly effect’ theory, meteorologist Edward Lorenz (1917-2008) asked whether the flap of a butterfly’s wings in Brazil could set off a tornado in Texas. This metaphor suggests that small events can lead to a ripple effect with a momentous result over time. Studies with herkogamic flowers reveal a new angle of the butterfly effect: by flapping their wings, butterflies may have much to contribute to the maintenance of biodiversity. 

Come in, she said, I’ll give ya shelter from the storm (Bob Dylan)

By Athayde Tonhasca

Life in the British uplands can be harsh, even for species adapted to cold temperatures and scarce resources. In these habitats, a mountain avens flower (Dryas octopetala) can be a safe berth for a fly or occasional bee. Insects get more than pollen and nectar from this plant: they also get warmth: the temperature on a mountain avens flower can be up to 30C higher than the surrounding air. 

Warm and cosy mountain avens flowers © Pantona, Wikipedia Creative Commons

Mountain avens flowers get warm because they follow the sun throughout the day, a phenomenon known as heliotropism or solar tracking. Moreover, flowers of mountain avens and some species from continental Europe such as alpine buttercup (Ranunculus adoneus) – from which we learned most of what we know about heliotropism – are usually bowl-shaped, so sunlight is reflected towards their centre. Heliotropism and flower form allow the plant to function like a satellite-tracking antenna, maximizing light interception.

 A mountain avens flower and a tracking radar © Robert Flogaus-Faust (L) and Daderot, Wikipedia Creative Commons   

But how do these flowers rotate to keep up with the sun’s position? 

We don’t know for sure, but can assume auxins are behind it. This group of hormones are involved in just about every aspect of plant growth and development, including phototropism (growing towards light).

Auxins and phototropism. Left: Auxin (pink dots) are evenly distributed in the plant’s tip. Centre: The repositioning of the sun causes the auxins to move to the opposite side of the plant. Right: The concentration of auxin stimulates cells to grow or elongate © MacKhayman, Wikipedia Creative Commons

Mountain avens’ heliotropism may be similar to what happens with the common sunflower (Helianthus annuus). In the morning, the stem and upper leaves of a young sunflower plant face east. As the day progresses, auxins move from the western to the eastern side of the plant. Auxins promote water absorption and tissue elongation, so the plant slowly bends westwards. The auxin gradient is reverted at night, and the plant is reoriented eastward. However, this cyclical movement stops when the plant flowers. So contrary to what some people think, sunflowers’ flowers do not follow the sun; they are always facing east (although wind or rain can change their position).

Solar tracking of a sunflower plant © Kutschera & Briggs, 2015. Phototropic solar tracking in sunflower plants: An integrative perspective. Annals of botany. 117. 10.1093/aob/mcv141

Heliotropism is an asset for plants with short growing seasons. The temperature of an alpine buttercup’s gynoecium (the female reproductive organs) can be 5.5°C higher than the flower’s surroundings. Heat accelerates pollen germination and the growth of pollen tubes; it also leads to heavier seeds and higher germination rates. So plants have greater reproductive success.

Heliotropic flowers’ absorption of solar irradiance encourages insects to visit and stick around, basking and foraging. The extra warmth increases their metabolism, and boosts their flight capability. Frequent and long-lasting insect visits are important for many upland plants, which cannot self-fertilise and rely mostly on flies for pollination. These insects lack pollen-carrying structures and, generally speaking, are much less hairy than bees. So the longer a fly frolics on a flower, the greater the chances it will get some pollen grains stuck to it. With luck, some pollen will be carried to another flower, and pollination will happen. A warm welcome pays off for plants and insects alike.

The hoverflies Melanostoma mellinum and Scaeva selenitica, upland flower visitors © James K. Lindsey (L) and Sandy Rae, Wikipedia Creative Commons

Making the right connections

When it comes to creating new areas of wildlife habitat and building a strong sense of community the Northern Corridor Community Volunteers are on the right track. Based in North Lanarkshire they can point to an impressive catalogue of pollinator-friendly actions, and much more besides.

Their aim is promoting, protecting and nurturing greenspace for community well-being in the villages of the Northern Corridor in North Lanarkshire.  They do this with a wonderful variety of projects which range from planting pollinator friendly native shrubs and wildflowers along a local path, to litter-picking and community growing, through to the production of information boards which highlight the importance of biodiversity

This wonderful community initiative has a big interest in the local environment and emphasised this by signing up to the Keep Scotland Beautiful ‘It’s Your Neighbourhood’ scheme which acknowledges and assists groups that seek to add value to their communities.

Now, listing all of the positive steps that the Northern Corridor Community Volunteers have taken would require more than a short blog, so below we have focussed on a few highlights to give a flavour of what they have achieved.

Working in partnership with the Seven Lochs wetland park they group has created eight pollinator habitats on areas of greenspace in Muirhead and Chryston. They have also worked with a local nursery group planting trees and pollinator friendly shrubs in their grounds, and have created a pollinator-friendly garden at a local community centre including a bug hotel which is much loved by the local children.

The group has recognised an opportunity in creating a new woodland using techniques which will restore natural plant communities on the woodland floor which in turn will prove extremely beneficial to pollinators.

That foresight is a hallmark of the group’s activities. They have lobbied their council for more relaxed cutting regimes on amenity grasslands and verges, the intention being to allow wildflowers to thrive, and pollinators to benefit.

Connectivity for pollinator species is high on the agenda these days and in Gartcosh the group stepped in to create a biodiversity area at the local station  – removing dogwood and replanting with native trees and flowering shrubs to support pollinators. In Chryston they complemented that approach by planting a wildflower and tree nursery to ensure a sustainable local supply of pollinator forage for the future.

That ‘eye to the future’ is evident in their involvement with ecological surveys and work with school groups. The recent award of £3000 from the Young Placechangers Ideas Fund is a welcome boost in this regard, and will enable the creation of a forest garden and help engage Youth groups in improving the environmental and biodiversity prospects of the area. Given that we faced a twin-challenge on the climate and biodiversity fronts this is excellent news.

With informal woodlands walks, a strong connection with Paths for All, and walking groups established in Moodiesburn their ambitions to embrace the health benefits of engaging with nature are clear. Plans for the future include a ‘Grow-Cook-Share’ healthy eating and food sharing scheme as well as the creation of an active travel hub.

The group certainly adopt nature-friendly practices at every turn. A good example came with their Woodland Creation Scheme where the use of natural grazing deterrents such as hawthorn and blackthorn is being employed to keep inquisitive roe deer at bay. 

As the above demonstrates this is a team that makes connections and plans for the future. I expect we will hear a lot more about the work of the Northern Corridor Community Volunteers in the future.

Find out more about the group on their website @ www.ourgreenspace.org

Follow the group’s activities on facebook @ https://www.facebook.com/groups/NCCVols/

A lethal bully loose in the garden

By Athayde Tonhasca

It’s a sunny mid-afternoon on a midsummer day in a British garden. A bumble bee wavers lazily over a patch of lamb’s ear (Stachys byzantina), as if considering whether its flowers are worth a visit. Before the bee makes up its mind, out of nowhere a black and yellow projectile collides mightily against it. The stunned bee falters and dips in the air, and is hit again. Struggling to stay aloft, it turns around and flees as fast as its battered wings allow it. If the poor bee could glance back, it would spot the aggressor now turning its attention to an unsuspecting honey bee.

The bumble bee and honey bee had the misfortune of entering wool carder bee (Anthidium manicatum) territory. Males of this species are notoriously aggressive towards perceived threats, either other males or any bee that may have an eye for plants from which female wool carder bees collect pollen, nectar or nesting materials.

A male wool carder bee and details of its menacing abdominal spines. © Bruce Marlin (L), Soebe (R) Wikipedia Creative Commons

Nowadays ecological research is focused on addressing specific questions, often within tight budgets and time frames. But there was a time when ecologists would sit down, watch and take notes. This old-fashioned approach has revealed the ruthless determination of male wool carder bees. Their charge sheet includes knocking down five bees in quick succession, and breaking the wings of bumble bees and honey bees. Victims have been knocked to the ground and mauled by bites and strikes from the attacker’s abdominal spines. Two males have been spotted hovering face to face like stags readying for battle, and when they clashed, the smaller bee fell to the ground, wings outstretched and abdomen vibrating (presumably dying or limping away afterwards). 

Such Rambo-like aggressiveness has a biological cause: polyandry (from the Greek for ‘many husbands’), which is when a female mates with several males in a breeding season. This mating system is uncommon among bees; for most species, females copulate once with a single male. But wool carder bees are polyandrous, just like honey bees. Monogamy is not an option for wool carder bees, and males have to deal with another headache: a physiological quirk known as ‘last male sperm precedence’. This happens when the male copulating last in a sequence of partners has a better chance of fertilising the female. So to assure paternity, the male must fend off any potential competitor and do as much mating as possible with any female in his territory: as often as every six minutes. Like most solitary bees, female wool carder bees lay eggs continuously throughout the breeding season, and they can mate up to 12 times a week.

For the female, it’s not all excessive attention from aggressive lotharios: she benefits from a patch of pollen and nectar free of competitors. She can focus on feeding and building her nest, which celebrated naturalist and entomologist Jean-Henri Fabre considered ‘quite the most elegant specimen of entomological nest building’. She begins by stripping the fuzz from the leaves and stems of lamb’s ear and related plants such as mint, deadnettle and sage (family Lamiaceae). She rolls the material into a ball – watch it – an operation akin to ‘carding’, which is the process of separating wool threads for the production of cloth.

A carding machine and a female wool carder bee collecting nesting material from lamb’s ear. © Wikipedia Creative Commons

She carries this bundle to a pre-selected cavity such as a hole in dead wood, a crevice in the mortar joints of a wall, or a hollowed plant stem. She will build the nest high up, where she’s less likely to stumble into spider webs. Once inside the nest, she shapes the collected fibres into a cell in which she lays an egg and deposits a mass of nectar and pollen to provide for the larva. She builds several cells in a single cavity, then seals up the entrance.

Rendition of wool carder bee life stages inside of a cavity nest. From left to right: pupa, larva, egg, and adult (female). © Samantha Gallagher, University of Florida Featured Creatures

This bee is found in variety of habitats, from gardens to open woodland and coastal sand dunes, where it collects pollen and nectar from a range of plants. It has a Palearctic origin (Europe, Asia and North Africa), but was accidentally introduced to north-western USA is 1963. From there, it has dispersed throughout the country and the Americas all the way to Uruguay. It is spreading in Britain too: once confined to southern England, it has established in Dumfries and Galloway and was recorded in Edinburgh in 2011.

The wool carder bee is a successful coloniser and the most widespread non-managed bee species in the world, which makes one wonder about possible consequences to other bees. Studies in America, where this bee is listed as an invasive species, have shown that the common eastern bumble bee (Bombus impatiens) avoids foraging near the troublemaker, but is not affected otherwise. The territory claimed by a male wool carder bee is no bigger than 1.3 m2, so there are plenty of available spaces; apparently the bumble bee simply looks elsewhere for food. Similarly in New Zealand, where the wool carder bee arrived in 2006, there has been no indication of harm to the native bee fauna. It looks like local residents are good at adapting to this feisty newcomer.   

Firm favourites – old and new

Two of our most popular plants, the primrose and the cherry, are in flower now. Perhaps we should add a third to that list – the dandelion. 

When we talk about primroses and pollinators we should stress that we are talking about the wild primrose, the pale custard-yellow plant that flowers amongst distinctive crinkly leaves in clusters beneath hedges, around woodlands and on verges. It is a particular favourite of bee-flies.

The Bumblebee Conservation Trust website covers this subject neatly and it is worth repeating their main point: ‘the brightly coloured primroses are mostly useless for bees, but the native wild primrose (Primula vulgaris) is often used by pollinating insects.

The name primrose has Latin roots, ‘prima rosa’ equating to the first rose in spring.  That’s a welcome nectar boost at a time of lean pickings for pollinators. One interesting, and often overlooked point, is that primroses have two almost identical types of flower. You can find out more about this distinction on the countryside info website

Variety is also a theme with flowering cherry trees too. Their saw-toothed leaves and five petal flowers are easy to distinguish. But as Dave Goulson noted in his excellent and entertaining book, The Garden Jungle,, ‘double’ flower varieties are useless for pollinators, whereas a standard cherry tree provides both food and drink for insects. Their enormous popularity ensures that most villages, town, cities and many gardens boast flowering cherry trees.

They are also popular in many countries, being the national flower of Japan, which gifted 200 cherry trees to Copenhagen to mark Hans Christian Andersen’s 200th birthday.

Many of the earlier, often white, but sometimes pink, cherry trees with lots of small blossom are cherry plum.  About the same time the native sloe flowers, followed by the more ornamental, usually pink, but sometimes white, Japanese cherry.  The native gean (= wild cherry) is one of the later flowering cherries.  In Scotland by the time they flower the sun is stronger, yet there is still snow on the hills.

The blackthorn is a member of the cherry family, and as the flowers arrive before the leaves, it is fairly easy to spot. A Gaelic proverb says às an dris, anns an droigheann ‘out of the bramble into the blackthorn’. It’s an equivalent of ‘out of the frying pan into the fire’

Bristling with long spiky thorns, this is not an easy plant to ignore. It is another concentrated source of food for pollinators.

Trees are an important source of food for bees and other pollinators by offering thousands of flowers in one place, and making gathering nectar and pollen more efficient. One of the village greens near our Battleby office is lined with cherry trees, which brim with bumblebee activity each spring, and nearby – on the banks of the River Tay – are several spectacular dense patches of blackthorn.

And finally to the much maligned, but increasingly rehabilitated dandelion (Taraxacum officinale)   Dandelions not only add a splash of bright, sunny yellow colour to verges, hedgerow bases, riversides and parks, they are a golden ticket for pollinators.

The problem for insects is that food sources are thin on the ground in early spring.  

A dandelion in bloom is a tempting restaurant for those insects seeking to stock up before they begin the job of raising the next generation.  Their long tap roots have made them unwelcome guests in many gardens and parks, and that is a shame for they are almost unrivalled in helping our pollinators. But perhaps the tide is turning as we acknowledge their pollinator worth.

The dandelion is known in Gaelic as Beàrnan Brìde ‘Bride’s indented one’, referring to its leaf shape and connection to a beloved saint. That’s a fitting place to end as the emergence of dandelions in March or April is indeed ‘heavenly’ for hoverflies, beetles, butterflies, solitary bees and the ever-popular bumblebees.  That’s why the dandelion should be tolerated by those who want to help pollinators.

Further reading re Dandelions: an excellent piece about dandelions and other flowering ‘weeds’ in Simon Leather entomology blog

‘You WILL pollinate me!’ Pushy characters of the plant world

By Athayde Tonhasca

When an insect visits a flower to drink nectar, eat pollen or collect it to feed its offspring, a few of the pollen grains become accidentally attached to its body. The insect moves to another flower and some of the pollen may get transferred to the stigma, kicking off the process of plant reproduction.

Such a passive, leave-it-to-chance approach is not good enough for some plants. Evolutionarily speaking, they have taken the matter of pollination into their own hands by forcing pollen onto visitors.

The mountain laurel (Kalmia latifolia) is a perennial shrub native to the eastern United States, and well known on this side of the Atlantic as an ornamental plant. The anthers of the mountain laurel flower are attached to small pouches on each petal. As the flower matures, the petals curve backward and pull the stamen filaments, which bend under tension.

A mountain laurel flower with 8 of its 10 anthers inserted into pockets in the corolla and held under tension © Derek Ramsey, Wikipedia Creative Commons

When a relatively large insect such as a bumble bee lands on the flower, it may pull at a filament, which springs up, releasing the anther from its pocket and launching pollen into the air at great speed: watch it. As most of the pollen is flung towards the centre of the flower, researchers believe this catapult device results in pollen grains being attached to bees and then carried to another flower.

Alfalfa or lucerne (Medicago sativa) has a similar mechanism: its stamen filaments are stuck together into a structure called ‘sexual column’, which is held under pressure inside two bottom keel petals that are fused together. When a bee pushes on those petals, the column is released, springing upwards and slamming into the upper petals. This process is called ‘tripping the flower.’ When it happens, pollen falls on the flower’s female reproductive organ and also on the bee, which then moves on to another flower. Some bees such as the honey bee don’t appreciate being whacked by a plant, so they avoid alfalfa flowers or learn how to get the nectar without tripping them. So farmers rely on the alfalfa leafcutter bee (Megachille rodundata) for crop pollination because this species is not bothered by a slap or two. Follow the whole story.

A bee visits an alfalfa flower, tripping it © Diana Sammataro, Sustainable Agriculture Research and Education

The tricks performed by mountain laurel and alfalfa are known as explosive pollen release. Similar devices have evolved in plants from several families, including our familiar Scotch broom (Cytisus scoparius) and gorse (Ulex europaeus). Insects are not always involved: sometimes plants rely on explosive pollination to launch pollen into the air so that it can disperse long distances and, with luck, drift towards a receptive flower.

Flower tripping is an ingenious mechanism, but it pales in comparison to the stratagem employed by Neotropical orchids in the genus Catasetum. These plants marvelled and puzzled Charles Darwin: ‘I have reserved for separate description one sub-family of the Vandeae, namely the Catasetidae, which may, I think, be considered as the most remarkable of all Orchids.’ (On the Various Contrivances by Which British and Foreign Orchids Are Fertilised by Insectsand on the Good Effects of Intercrossing, 1862). 

A bit unusually for plants, Catasetum orchids are either male or female – they are dioecious species. They have strong sexual dimorphism, that is, male and female flowers look different: so much so that male and female plants were once considered to be separate species. These flowers produce no nectar, but they secrete fragrances that are collected by male orchid bees (tribe Euglossini), possibly to be used for chemical signalling to females: we don’t know for sure.

Male (L) and female Catasetum arietinum inflorescences © Brandt et al. 2020. AoB PLANTS. 12(4).
Male (top) and female Catasetum arietinum flowers © Brandt et al. (2020). AoB PLANTS. 12(4).

When a male orchid bee lands on a male Catasetum flower, it touches a pair of antennae-like structures that trigger the shooting a blob of sticky pollen known as pollinium against the unsuspecting visitor. It happens with such force that the poor bee is sometimes knocked off the flower. Watch the stunning (literally) speed of pollinium ejection, which can reach 2.6 m/s. For comparison, a pit viper, another Neotropical forest denizen, strikes at 1.6 m/s. We don’t know how the orchid does it, but apparently changes in electrical potential and tissue turgor are involved, similar to what happens with the sensitive plant (Mimosa pudica). Incidentally, Darwin never observed Catasetum flowers in the wild, but he reasoned that their pollen ejection must be related to bee pollination.

A male orchid bee ©Alejandro Santillana, Insects Unlocked, Wikipedia Creative Commons

The bee is not only surprised, but ends up with a hefty load as well: a pollinium can make up 23% of its body weight. The bee does not like this rough treatment one bit, so he tries to brush off the pollinium, but rarely successfully. He may also avoid visiting another male flower, which suits the orchid just fine: the bee is likely to seek a female flower, which does not have that pollen-spitting attitude. By doing so, there is a good chance the pollinium will lodge itself into a specialised receptacle of the female flower, and the orchid is fertilised.   

Two orchid bees, Eulaema cingulata (L) and E. meriana bearing pollinia of Catasetum pileatum © Romero-González et al. 2017. Harvard Papers in Botany 22(2): 145–155

Darwin’s work with orchids and their relationship with visitors intended to test some of the ideas from On the Origin of Species such as coevolution. He could never have imagined that his studies would inspire H.G. Wells to write the tale of a Mr Winter-Wedderburn, who buys a strange orchid and tells his housekeeper: ‘There are such queer things about orchids. Darwin studied their fertilisation, and showed that the whole structure of an ordinary orchid flower was contrived in order that moths might carry the pollen from plant to plant’. But science turns to horror when the orchid flowers: it produces a scent that makes Winter-Wedderburn pass out. The orchid wraps its roots around his neck to suck his blood, but luckily the housekeeper is at hand to rescue the unfortunate gardener from the vampire plant. Wells’ story was translated into several languages and inspired numerous imitators into a new genre of science/horror fiction that is still around today: the man-killing plants. 

Herbert George Wells: ‘The flowering of the strange orchid’, The Pall Mall Budget, 1894

The reception of Wells’ story reflects the fascination we have with Nature and its mysterious ways. Certainly much more remains to be discovered about plants and their pollinators, so many a fantastic tale can be written.

 

Hello Taynish – I’ve missed you!

By Caroline Anderson

It’s been hard hasn’t it?  I think this lockdown has been more difficult than the last one, apart from not seeing my family for a very long time which has been hardest of all, I’ve also missed insects and haircuts in that order – and believe me I’ve really missed haircuts!   However with the improvement in the weather, the longer days and hairdressers being opened again things are looking up! 

I ventured to Taynish towards the end of March and though ever hopeful, I wasn’t really expecting to see anything, but as always Taynish delivered with a first sighting of a Small Tortoiseshell butterfly this year followed closely by a bee, what joy that brought.

As usual the first stop was the boardwalk – again ever hopeful but probably about 6 weeks too early for damselflies.   However the lochan was absolutely alive with the sound of toads, it was very calming just to sit and listen for a while.

Then down at the picnic area more butterflies and bees, and a hoverfly of unknown origin, but which made its presence known by hovering right in front of my face – it seemed as curious about me as I was about it. 

The next visit to test out the new road down to the car park (it’s marvellous) was made last Friday.   There was a noticeable difference in the number of leaves on the trees and flowers on the plants – lovely to see patches of wood anemone and wood sorrel and of course the ever faithful primroses. 

Again the butterflies were out – but more Peacocks this time all fresh and new their markings were so bright and eye-catching.

I also spotted this fly, which I am assured is a male Tachina ursina. 

Lots more activity on the bee front too – you could hear the buzzing from the tree tops which was glorious, they were also very active on the whin.

So after a couple of visits to Taynish NNR (and a haircut) I still have seeing my family to look forward to.  All in all though I am feeling hopeful with good Taynish fresh air in my lungs and lots still to emerge, here’s to the next visit. 

On a more serious note, the positive impact nature can have on your mental health cannot be underestimated. Get out there – even if you have to force yourself – get outside, breathe it in, listen to nature going about its business, and I guarantee you will feel better.

Down to Earth

By Athayde Tonhasca

Of the more than 20,000 known species of bee in the world, most (~80%) are solitary, that is, each female constructs and provisions a nest by herself. And most (~70%) nest underground; these are fossorial (from the Latin fossor for ‘digger’), a term applied to animals adapted to digging and living underground. In the UK, about half of the 250 or so bee species are fossorial. They are better known as ‘mining bees’ or ‘miners’.

Common furrow bee (Lasioglossum calceatum) and Gwynne’s mining bee (Andrena bicolor), two widespread fossorial species © gailhampshire, Wikipedia Creative Commons

There are many types of mining bee nests, but a typical design comprises an entrance surrounded by a small ‘volcano’ of excavated soil, known as a tumulus. This entrance leads to a tunnel, which may branch into cells. The female bee lines these chambers with a waterproof waxy or paper material, or sometimes with mud, pebbles or pieces of leaves and petals. She will then stock each cell with a ball of pollen and lay an egg on it. The larva will feed on the pollen until it is ready to emerge as an adult. 

A tawny mining bee (Andrena fulva), a regular occupier of garden lawns, and its nest entrance © entomart (L), Sarah (R) Wikipedia Creative Commons
Multiple life stages of the alkali bee (Nomia melanderi) © Art Cushman, USDA Systematics Entomology Laboratory, Bugwood.org

Bees and their pollination services have been the subject of numerous initiatives around the world, largely focused on safeguarding pollen and nectar. These plans are laudable and helpful, but fall short. All the food in the world is no good to bees if they cannot build nests and raise their young.

Underground nesting does not sound like a tricky housing specification – after all, we are surrounded by solid ground. But the properties of a patch of earth can determine whether a mining bee can move in. Many fossorial bees need bare ground at a certain angle, so that nests are adequately warmed by the sun and protected from flooding. The physical properties of the soil must be just right: too hard, and the bee can’t dig; too soft, and the nest may collapse. Even soil acidity and organic matter content are important for some species.

This fussiness about nesting spots may help explain why females of some species nest near each other despite the risk of attracting parasites. These nest aggregations may be thousands strong, all sharing an area of suitable habitat – which could be a section of a well-trodden footpath or dirt road: these bees don’t mind sharing their space with us.

An aggregation of tawny mining bee nests © Africa Gomez, BugBlog

Mining bees and other solitary bees pollinate wild plants and crops, especially fruit trees such as apples. Despite the importance of these bees, conservation programmes have paid scant attention to their dietary needs, and even less to their nesting requirements. This omission is partially understandable because we know little about bees’ biology and behaviour. But broadly speaking – and this is certainly not applicable for all species – bare ground creation is a promising management option. This can be done by digging and compacting the soil on field margins, or by scraping the ground surface with farmyard machinery, ideally on south-facing slopes. The vegetation should be kept low by mowing or trimming.

Bee nests in a surface scraped with a digger © Nichols et al. (2020) Conservation Evidence 17: 15-18

In some situations, all it takes is to leave bees alone. Land managers may be tempted to ‘tidy up’ exposed ground by planting or landscaping it. By doing that, a well-intentioned practitioner may destroy whole colonies of mining bees.

Eroded ground, prime real estate for mining bees

In other cases, mining bees need protection. The Northern colletes (Colletes floralis) is one of the rarest British bees. It is present in low densities in continental Europe, but the bulk of its population is confined to coastal areas of Ireland and Scotland, with a couple of locations in England. In Britain, the greatest threat to this bee is the destruction of its nests, which are built in bare or sparsely vegetated coastal sand dunes. Housing, golf courses, motor racing tracks, marinas, wind farms, sand quarries and sewage treatment plants are all wearing away Northern colletes habitat.

Bees and people can often coexist, but sometimes we need to give them a break. 

The Northern colletes © Arnstein Staverløkk, Wikipedia Creative Commons

Norway’s pollinator progress

The Nordic and Baltic nations share Scotland’s desire to help pollinators. Last November, a virtual gathering of entomologists and environmentalists celebrated the work taking place to help pollinators in Northern Europe. In our blog today we take a look at the Norwegian experience.

The Norwegian approach to a pollinator strategy echoes our experience in Scotland.  Once the challenges facing pollinators were acknowledged, they produced a strategy identifying actions with a strong emphasis on partnership with municipal authorities, volunteer groups, individuals, beekeepers, science and research groups, energy sector, transport bodies, environmental bodies and farmers. 

Their strategy identified influencing land management as crucial for success. Parks, gardens, green infrastructure, meadows, coastal heaths, woodland margins, road verges and agricultural settings were all identified as areas where pollinator-friendly practices would have a huge impact. 

La Humla Suse is one of the key organisations working to help pollinators in Norway. Its primary goal is to create and improve habitat for bumble bees and they have a range of activities to encourage Norwegians to get involved. They organise guided bumble bee walks, give advice to farmers, local authorities and communities, help to create bee-friendly streets, and offer courses for nursery and school teachers. Their latest project is set to improve transport verges throughout Norway.

Campaigns such as the ‘Buzzing gardens’ aim to explain why pollinators are important, and  outlines what individuals can do on their own doorstep to help. Several urban towns, including Oslo, Trondheim and Moss, have implemented pollinator-friendly approaches, to the delight of their residents. 

Oslo’s  ‘bee highways’ are rather like the B-Lines here in Britain. The project sees the creation of feeding and travel routes through Norway’s capital via small meadows, floral verges, rooftop gardens and planted containers. There are moves to transform the Mindemyren district of Bergen into a greenspace haven.

Others have picked up the challenge. There is a drive to encourage the introduction of floral strips along farms, the creation of meadows adjacent to transport networks and a growing raft of advice on what to plant for pollinators. 

Of the 35 species of bumble bee in Norway, five are listed as near threatened. Indeed across Norway some 200 pollinators are on the national red list, of which around 30% are bees. To reverse these figures a bold strategy and a mixture of tactics is necessary and the indications are that change is afoot.

Astrid Loken, a Norwegian entomologist and member of the resistance movement, would have been in the vanguard promoting help. Her 1971 Studies on Scandinavian bumble bees is the highlight of a life-time devotion to the subject. The first female member of the Norwegian Entomological Society and a noted academic, she would have been thrilled to know that almost 200 delegates gathered for a Promoting Pollinators conference.  Thanks to her drive and influence we can celebrate progress built on solid foundations years later.

Find out more:

Read : Norwegian Pollinator Strategy is available in English.

Visit : La Humla Suse website

Enjoy : Scandinavian / Baltic States webinar on pollinators.  


Things move on

So it’s farewell to snowdrops, winter aconites, and crocus. Now we welcome coltsfoot, lesser celandine and butterbur to the floral stage. All have an appeal for pollinators, and deserve a very warm welcome.

Coltsfoot can be mistaken for a dandelion at first glance.  But look closely and you will see differences. The  coltsfoot’s stem is a give-away;  it is like a close up view of fish-scales. In Sweden the plant was known as Hästhov (horse hoof), reflecting the shape of the scales. Leaves come later, and initially the bright daisy-like yellow flowers lure early pollinators including queen bumble bees and a variety of flies.

Named Tusilago or fárfara, in Spanish coltsfoot also had the equivalent popular name of ‘pie de caballo’ or ‘uña de caballo’, which means ‘horse hoof’ or ‘horse nail’ – there seems to be similar folklore names in other parts of Europe (the Portuguese equivalents are arguably more fun and go along the lines of ‘mule hoof’ or ‘donkey hoof’).

Like many plants, coltsfoot was used as an early medicine. You might have thought those scaly stems would have put folk off.  However, it was reckoned to be a cure for colds, coughs and sore throats.   But eating any part of this plant causes an array of illnesses, including liver damage. 

The coltsfoot was also viewed at one time as a substitute for tobacco, and smoked! This strikes me as likely to have simply made it even more useful as a cough remedy, a vicious circle perhaps! In some quarters the sight of coltsfoot apparently indicated that somewhere, somebody was about to experience justice being done.

If dandelion and coltsfoot are often confused, the same can perhaps be said of winter aconite and lesser celandine. The yellow flowers of the latter are associated with the confirmation that spring is truly here. The glossy petals are vivid yellow in the centre but often fade to near white at the tips.  The distinctive heart shaped leaves are perhaps the most reliable sign of this plant.   Lesser celandine is widespread, being found in woods, on roadsides, beneath hedges and along river banks. The petals, and there are usually nine, remind many of buttercups and are noticeably pointy.

Flies as well as bees pollinate these flowers. There are ancient tales of the plants being crushed and applied to bleeding wounds. Others refer to it by the name of pilewort and as you might suspect it was used to tackle haemorrhoids.  Remains of the plant have shown up in the Mesolithic middens on Oronsay. In pre-war Germany it was grown to feed livestock, such were the prices for conventional foodstuffs.

Finally, to the delightfully named butterbur . This rather striking plant grows in clusters, and there are several near our Battleby office just north of Perth. The star-shaped flowers sit at the end of comparatively thin stalks. The leaves eventually become so big that they were once used in some parts to wrap butter.

The plant has an interesting male-female divide and which might even be related to how our ancestors actively looked after honey bees.  Further information on the butterbur species can be found in ….was the feature of a NatureScot (then Scottish Natural Heritage) blog. This is the explanation behind the peculiar distribution … “One of the most fascinating things about the butterbur is the odd distribution of the male and female plants.  For some reason male plants have a wider distribution, with almost all butterbur in the south of England being male.  How could that be?  The answer could be that male plants produce both nectar and pollen at a time of year when few native species are flowering.  There is a suggestion that in the past the male plants were deliberately moved about as a source of food for honey bees during the early spring.  We might buy our sugar from shops, but in the past honey was highly valued and used for sweetening so planting butterbur to help the bees is a plausible explanation.”

The star-shaped flowers sit at the end of comparatively thin stalks. The leaves start as delicate under-stated heart-shaped elements, but eventually become so big that they were used in some parts to wrap butter.

The non-native, and often invasive, white butterbur is more abundant at this time of year, particularly beside rivers. It has a couple of interesting names in Gaelic – gallan mòr is the more common of the two and means ‘big stalk’, the other is puball beannach meaning ‘peaked tent’. The Spanish name most commonly used for butterbur is Petasita from Petasites hybridus. Petasites is the generic name derived from the Greek ‘petasos’ meaning “wide brim hat”, in recognition of the large leaves of the plant.

These plants aren’t what you would classify as garden plants. But at this time of year they do add a lovely blast of colour on rivers, verges and margins.