May the Force be with the bee

By Athayde Tonhasca

If we are asked how a bee finds a flower, we think of smells, colours, shapes and textures. These are important sensory signals, but there is another one whose relevance is just beginning to be understood: electricity.

It has long been known that the platypus, some fish and amphibians, as well as some ants, cockroaches, mosquitoes and fruit flies have the ability to detect external electric forces. However, vertebrates need water as a conductive medium, while most insects respond only to unusually strong electric fields such as those generated by high voltage power lines. Bumble bees however have a sparking story to tell. 

We do not notice it, but our planet is an immense electrical circuit. On a calm day, the air is positively charged, while the ground surface has a negative charge. Now and then the equilibrium of charges is disturbed by lightning bolts or a minor shock from a car door, reminding us we are surrounded by electricity.

The negative charges accumulated on the planet’s surface extend to any object connected to the ground, plants included. So flowers have a slight negative charge in relation to the air around them. As a bee buzzes along in search of food, electrons are stripped off its body by friction with the air, leaving the bee positively charged. When the bee lands on a flower, some of the negatively charged pollen grains stick to the bee, sometimes jumping from the flower even before the bee makes contact. So electrostatic forces are a great aid to pollination.

An electrifying encounter: a positively charged bee approaches a negatively charged flower. Images in the public domain.
Pollen clinging to a sweat bee. © Pixabay.

But flower power reaches shocking levels for the buff-tailed bumble bee (Bombus terrestris), and probably for other bumble bees as well: they are able to sense the weak electric field around a flower. No one knows exactly how they do it, but mechanoreceptive hairs must be involved. These special hairs are innervated at their base, so they detect mechanical stimuli such as air movement and low frequency sounds. Apparently, the flower’s electrical field moves the mechanoreceptive hairs of an approaching bee, similar to the way a rubbed balloon makes your hair stand on end. This hair movement is processed by the bee’s central nervous system and gives information about the shape of the electric field. It is as if the bee ‘sees’ the flower’s electrical aura. 

Bumble bees’ hairs provide thermal insulation, collect pollen and help bees sense air motion, sounds and electricity. ©Kevin Mackenzie, University of Aberdeen. Attribution 4.0 International (CC BY 4.0).

But bumble bees’ capacity to detect electric forces may go beyond recognising flowers’ sizes and shapes: they could use the information to maximise foraging trips. Once a positively charged bee lands, the flower’s electric field changes and remains changed for about two minutes after the bee leaves. Researchers believe that an altered field warns the next bee that the flower is temporarily depleted of nectar; it’s like turning off a ‘we are open’ neon sign. So the next bee may as well buzz off to another flower with sufficient negative charges and a decent volume of nectar. 

Bees and other insects detect ultraviolet and polarized light, and use magnetic fields for navigation. Sensing electricity is one more way their world is experienced radically differently from ours.

A colourful banquet

After several months of the cold and prolonged darkness of winter it’s an eagerly anticipated delight to see the first sparkling flowers of the year emerge.  Amongst the highlights are surely twinkling snowdrops, glossy winter aconites and vivid crocus.

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For many people the first glimpse of snowdrops is a sure sign that spring is coming. The dazzling white flowers are a boon for insects and this is a plant that requires absolutely no maintenance.  There was a misconception at one time that snowdrops didn’t produce seeds, but they can if there are pollinators about and for any emerging queen bumblebee snowdrops could be a life-saver. Bumblebee Conservation Trust point out that in some areas the buff-tailed bumblebee is active in winter and that snowdrops can be a great source beyond the likes of Mahonia and winter-flowering heather.

 

Snowdrop have another endearing quality, they frequently evolve into patches or drifts. As you might expect given their eagerly anticipated early flowering they have an interesting social history. Once strongly associated with Candlemass, which falls 40 days after Christmas, they had a less celebrated association with churches as they were often planted around graveyards which for some meant that snowdrops were associated with death.

 

From the white of the snowdrop to the golden yellow of the winter aconite. This low plant can create a stunning display of yellow at what is often a grey time of year.  It certainly lifts the spirits of many and it isn’t uncommon to see it flowering next to snowdrops making for a lovely sparkling display.

Winter aconites. ©Lorne Gill

The winter aconite, is reckoned to be a native of south west continental Europe and, just like the snowdrop, is naturalised in the UK.  It has nothing to do with the ‘real’ aconite.  Instead it’s a member of the buttercup family and loves deep deciduous woodland where it flowers before the tree canopy opens.

 

Without tree leaves “getting in the way” light can get down to ground level even at this time of year making the flowers very visible.   The flowers reflect UV light suggesting that they are adapted to attract pollinators which can see the UV spectrum. As an early source of nectar winter aconite has a role in helping insects that venture out before spring is fully in swing.

 

And so to crocuses, where the colour range increases significantly. Spring-flowering crocus is a great source of early nectar and pollen for foraging bees and flies as the days begin to warm up. Indeed the sight of pollen-sprinkled bumblebees on purple crocuses with their vivid yellow stamen is an increasingly popular macro photograph these days.

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As with many plants we can’t be 100% sure of how the crocus made it to Scotland, but it is reckoned that the bulb originated from parts of western China, the Middle East and Mediterranean parts of Europe. Again this isn’t a difficult plant to care for and provided the bulbs are not sunk too deeply they have a chance of doing well, and you certainly don’t need to tidy up after them once they have flowered. I do however note that I get the odd squirrel digging up the bulbs!

 

If you want to get your garden or container buzzing, these popular plants might be just thing for you. They will add a dash of early colour, and our pollinators will certainly benefit.  Enjoy them this year if you have them, and perhaps plan for next year if you don’t!

Marvellous meadows

East Dunbartonshire Council are one of a number of councils converting much of their bland amenity grassland into wildflower meadow.  Under the expert influence of Jackie Gillespie they have made great strides, and as I found out recently, they aren’t finished yet.

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I visited four locations around the Strathkelvin area and saw at first-hand how they are slowly but surely delivering a transformation that is going to be great news for pollinators. And I rather suspect that people are going to like it too.

I started my tour at Lennoxtown in the shadow of the Campsie Fells and the popular cycling challenge that is the famous Crow Road.  Bathed in sunshine down by the River Kelvin I came across a stunning wildflower meadow. This rich meadow is just a few  years old and in summer a glorious technicolour feast for pollinators. The ever-popular John Muir Way runs alongside the meadow and the area is well noted locally. Asking for directions revealed a degree of local pride in ‘our meadow’

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During my visit I saw red-tailed bumblebee, various hoverflies and a generous smattering of butterflies. It was clear that as a source of food the meadow was doing a great job.

A quick hop along the road and I found myself in Bearsden’s Cluny Park. Here a four-year old meadow was perhaps going over, but had,  judging by the comments I heard, made a huge impression locally. Sandwiched between the Bears Way cycle route and busy A81 and has become something of a local landmark. The weather was sunny and fine, the mix of grasses were swaying in the gentle breeze and cyclists were gliding past … all in all a most tranquil scene on the fringes of Scotland’s largest city.

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If the Bearsden meadow is highly visible then the equivalent in Torrance could accurately be described as being ‘tucked away’. This is a new meadow so at the moment the planting has just been completed. As anyone who knows about meadows will testify, you need patience. It isn’t much to look at just now, just a series of pock marks on the grass but given time an array of wildflowers will pop through.  No two meadows are alike, no single meadow is the same year on year … and always there are challenges. Here the challenge might be the proximity to the River Kelvin and the banks of rosebay willow-herb patiently poised for areas to spread into.  Time will tell.

My final port of call was Milton of Campsie, where like Torrance, works are at an early stage. I feel the folks of Milton of Campsie are on the verge of being spoiled, for the ambitious folks at East Dunbartonshire Council have gone for not one, not two, but three meadows. The new meadows promise to give pollinators some great forage in addition to the plethora of gardens that are a proud hallmark of this community.

Creating meadows is a sure-fire way to help pollinators.  Tackling historic loss of habitat, and a shortage of food, is an incredibly practical step to take to help deliver Scotland’s pollinator strategy.   It hasn’t been easy, and it may not look at its best yet, but in time what East Dunbartonshire Council have done will be mightily well-received – by people and pollinators.