Butterbur's irresistible allure for honeybees

Butterbur Petasites hybridus is a wonderful source of nectar and pollen for bees in spring - especially honeybees. These were feeding on the flowers of a large patch of the plant along the banks of the river Wear at Wolsingham in Weardale.

More about honeybees and the strange distribution of male-only clones of butterbur in today's Guardian Country Diary.

Honeybees in January

Two days ago we had snow on the ground and freezing winds. Then the thaw arrived.

Today, at mid-day, it was like spring, with warm sunshine coaxing out honeybees in our son's back garden at Winlaton Mill near Gateshead.

The bees were busy collecting pollen from Viburnum tinus. There as also a bumblebee out, but it flew away over the fence before I could see what species it was of take a photograph.

This one had full pollen baskets

More on winter honeybees here

In praise of some non-natives

Wildlife gardening evangelists frequently exhort us to plant native species in our gardens - quite rightly, as there are indeed many native plants that are decorative and provide valuable resources for insects and their larvae. 

But when it gets to this point in autumn the choice of flowering natives is pretty narrow. There's ivy, which is certainly a terrific source of pollen and nectar for insects and also food plant for holly blue butterfly larvae, but that's about it  - other that a few late hogweed flowers and yarrow, which flower up until the first frosts but don't bring much colour to a garden.

So that's when Michaemas daisies Aster amellus, whose natural range extends across southern Europe into Asia, come into their own. Whenever the sun shines the Michlaelmas daisies in our garden attract a constant stream of visitors, including ....





.... hoverflies, like this Heliophilus pendulus

..........honeybees ......

.............. small tortoiseshells ............

.............and red admirals, all photographed in the space of a few minutes at the end of last week.

Marigold Calendula officinalis, which originated in southern Europe, provides similar services for butterflies throughout autumn.

Buddleia davidii, the famous butterfly bush from Central China and Japan, has - until recently - been a favourite amongst wildlife gardeners as a nectar source for butterflies, even though it usually finishes flowering long before the late autumn generation of small tortoiseshells, peacocks, red admirals and commas get into their stride. These days conservationists give B.davidii the thumbs down, on account of its invasive tendencies, but there is a much better Buddleia alternative - B x weyeriana, which is an interspecific hybrid between B.davidii and B.globosa and has very attractive pinkish-orange flowers and none of its parent's tendency to seed itself around prolifically. It's extremely hardy and continues to flower long after the first frosts, offering a 'last-chance saloon' for any insects that need to top up with nectar before going into hibernation.

Red Admiral hairy eyes

One of the pleasures of macrophotography is that you tend to notice things in the captured image that you'd never be aware of otherwise.

Until the colder weather arrived a couple of days ago we had several red admiral butterflies in the garden. I took some extreme close-ups of them, while they were feeding on ripe pears, and noticed in the images .....

.... that their eyes have this strange hexagonal pattern. Looking closer still, it's clear that .....

.... the eye surface is hairy and it looks like it's the pattern of hairs, located in between the individual ommatidia of their compound eyes, that is responsible for those large pale hexagons. A comparison with eyes of other common butterflies, like...

..... this small white, shows a pattern of darker patches on the eye but not a hint of hairiness around the ommatidia.

So I wonder what the hairs' function might be? Maybe they enhance flicker vision - the sensitivity of compound eyes to movement of objects across the field of vision............? 

Hairy eyes are not uncommon in insects - click here, for example, to see a scanning electron micrograph of a honeybee's hairy eye. Another possibility of that the hairy surface might stop pollen sticking to the eye surface in these flower-visiting insects.........

Making sense of smells

Today's Guardian Country Diary is about the close link between scent and memory, about the way in which a whiff of a natural odour can transport us back to personal memories of  our past.

Years ago, when I was learning to identify plants at school, a teacher made us crush and smell a piece of all the plants that we found, emphasising how important the smell of  plant can be in identification. There are many that can be named with your eyes closed, like..........

..... hogweed, for example. Just crush one of the seeds between finger and thumb and those oil glands - the brown stripes on the seed coat - release a pungent, slightly fruity aroma that for me is one of the smells associated with the drift from summer into autumn.

Our sense of smell is quite limited compared with that of many other animals, particularly insects. There is a whole scent landscape that we are unaware of that includes mating pheromones and scents that insects associate with food sources. Their scent perception is concentrated in their antennae and you can see how important these are just by watching a honeybee at work.

If you look closely at this one, exploring a day lily flower, you can see that it's touching the pollen with its antennae before feeding ....

...... and this one, visiting Astrantia flowers, is constantly touching them with its antennae while it feeds.

Scent is an important means of communication in bees. They label flowers that they've visited with secretions of their Nasonov glands and also use scents from the same gland to make other workers aware of food sources.

Scent production in flowers is a complex process too. When we poke our nose into a rose to appreciate its fragrance we are using a very crude instrument compared with an insect antennae. Chemical analysis of rose fragrances reveal subtle but distinct differences between the scent of petals and the scent of the pollen; the former is a general attractant to insects whilst the latter orientates them for the true purpose of the visit, to pollinate the flower, once they have landed.

Insect sensitivity to scent is also far greater than our own, with moths being able to detect the scent of nocturnal flowers like honeysuckle from long distances down-wind.

Our ways of describing subtle differences in scent in the English language are as crude as our sense of smell. When we describe an aroma we tend to use general terms like 'pungent' or 'acrid' or 'sweet' or 'foetid' and then qualify them by adding an analogy to another scent that's commonly experienced by fellow humans - like the scent of a herb, foodstuff or excreta.  Our language is seriously limited when it comes to describing, in absolute terms, subtle differences between the scents we can detect. Which is why, I guess, that wine tasters resort to such tortured terminology when they are describing the bouquet of wines and often lapse into incoherence.

 To see what I mean, watch this..........

But for something even more amazing in the world of insect olfactory senses, take a look at this post on Africa Gomez's BugBlog which reveals how butterflies detect scents with their legs and feet. 

Imagine what life would be like if we could do that .........

Gold standard

If I had any sense I'd probably have dug out the dandelions in the gardens long before now because they seed themselves so prolifically, but instead I've been watching the constant stream of bees - with their pollen baskets stuffed full of orange dandelion pollen - visiting the flowers all afternoon. There are golden drifts of dandelion flowers everywhere just now - along road verges, on waste ground and in pastures - and every year they provide a reliable source of vast amounts of pollen and nectar for bees.

The strange thing is, though, that dandelions don't need nectar, pollen or pollinators to produce a full crop of seeds - for the reason why, click here.

Africa Gomez, over at Bugblog, has more pictures of some of dandelions' many insect visitors in spring.

Riotous spring

Any doubts that spring had finally arrived were dispelled yesterday by a honeybee trapped in our greenhouse (and safely liberated) .........

............ celandines coming into bloom all over the garden ...........

........ and frantic frog activity in the garden pond.

Since the frogs first emerged from hibernation the pond has frozen and thawed several times, but the chilly spring doesn't seem to have .....

.... dampened the frogs' ardour.

By this afternoon most of the females had left the pond, looking somewhat slimmer and leaving behind massive quantities of frog spawn.

Theft in the flower border

Columbines are awkward flowers for bees to visit. They can reach the pollen by hanging from the stamens that dangle from below the flower, but the nectar is only accessible to insects with very long tongues. The nectar is secreted from the tip of those tall, tubular nectar spurs above the downward-pointing flower.

But within a few hours of opening all the nectar spurs in the columbines in my garden have holes ripped in them ............... and here....

..... is the culprit. Bumblebees must be able to smell the nectar inside the nectar spurs and quickly learn to short-circuit the legitimate route for extracting it, by simply using their powerful jaws to chew a hole in the nectar spur. Then it's easy to use their short tongue to suck out the nectar.

It always seems to be nectar-thieving bumblebees that chew the holes but honeybees soon learn to use this breach in the flower's security system.

When the columbines have finished flowering the devious bumblebees turn their attention to thieving nectar from broad beans, by chewing holes in the back of the corolla tube and so avoiding the effort and wear-and-tear that's involved in forcing their way between the petals at the front of the flower.

More items on flower pollination here.

More items on bumblebees here. 

Honeybee Housekeeping

Yesterday we found about 20 honeybees dead in the snow near some hives in Durham City, and immediately jumped to the conclusion that some new catastrophe was befalling these useful insects. But a bit of Googling around beekeepers' web sites suggests that it ain't neccessarily so.

Apparently dead bees are quite common around hives in winter but when they are scattered in the grass and withered leaves they usually pass unnoticed. Opinion seems to be that they are there for two common reasons for this winter mortality. One is that on sunny days, even in the depths of winter, members of the hive remove the corpses of dead bees and dump them some way away, as part of their winter housekeeping. The other possibility is that bees' metabolism ticks over during winter and waste material accumulates in their hind gut, so they occasionally leave the hive on bright days just to defaecate; some don't make it back before the cold gets to them. Given that all of these dead bees were in a few metres of one another, I'd go for the former explanation in this instance.

Plant Public Enemy no.1

Japanese knotweed Fallopia japonica tops the table of alien, introduced plants that have become invasive weeds in Britain. Its phenomenal capacity to spread via deep, tough underground rhizomes and its resistance to herbicides, coupled with its tendencies to undermine building foundations, footpaths and roads, have created thriving businesses that specialise in trying to keep it under control. Introducing the plant into the wild is an offence and although it's not illegal to cultivate it in a garden, disposing of it when it begins to overwhelm your plot is a major problem, as Japanese knotweed-contaminated soil is classified as controlled waste and has to be removed by specialist companies. In the past much of the spread of the plant has probably been due to gardeners dumping plant waste, beside roads, rivers and canals. The fact that mortgage lenders are now refusing to lend to buyers of houses with Japanese knotweed in their garden should be sufficient deterrent for anyone contemplating planting it in their plot.

Since our Victorian ancestors first introduced it into their landscaped gardens it has spread around the country via fragments of rhizome in soil, especially in urban waste ground where it often forms four metre tall forests. Apparently, 137,500 tonnes of contaminated soil had to be removed from the London Olympics site alone, before construction could begin and, nationwide, about £150 million is spent every year trying to  control Japanese knotweed. One ray of hope for those seeking to bring it under biological control is that trials of a plant psyllid bug called Aphalara itadori, recently approved for release into infested areas, indicate that this insect could weaken the plant and make other forms of control, like herbicides, more effective

So, with all its destructive tendencies, is there anything positive to say about this aggressive invader? Well - excuse me while I reach for my flak jacket - there is. It's a magnet for honeybees. This fine specimen, that I photographed last weekend growing beside a pavement in Newcastle, near the Ouseburn, was humming with them. It's an ill wind, etc., etc................. 

Honeybee in Disguise

The first time I saw one of these bees with a distinctive band of white hairs along its thorax I spent some time leafing through field guides unsuccessfully trying to name it – until I realised that it was a honeybee that had been feeding on Himalayan balsam flowers (see http://cabinetofcuriosities-greenfingers.blogspot.com/search/label/Himalayan%20balsam). When the bee pushes its way into this flower to reach the nectar the hairs on its thorax pick up white pollen from the stamens that are in the roof of the floral chamber. As it backs out it brushes the stamens away exposing the stigma, ready for the next pollen-laden visitor to the balsam flower to deliver its stripe of pollen to the sticky stigma. I've also seen wasps with tell-tale white thoraxes which have evidently been collecting nectar from the same source. I photographed this ‘striped’ honeybee today on wild carrot, after it had exited the Himalayan balsam flowers nearby.

The importance of the commonplace

Naturalists tend to be obsessed with rarities but it’s the common species that are the foundation of all ecosystems. The billions of dandelions flowering now – common and so taken for granted - provide a reliable source of pollen for honeybees and other insects just when they need it most. Rare species are generally those that are at the natural limits of their range of climatic tolerance anyway, and so come and go according to the vagaries of climate, but it seems to me that we should be most concerned when common species that play a pivotal role in ecosystems become less common – that is a symptom of potential catastrophe. Loss of old pastures has led to a rapid decline in cowslip populations in many parts of the country, but this can be reversed. I found this wonderful display of cowslips – deliberately seeded – just outside of Durham city today. This was a patch that was roughly the size of a medium-sized back garden; imagine what a five acre pasture with a population of cowslips like this would look like. They do still exist - I know of a few in the north east, although none are quite as denslely populated with cowslips as this. The wild plant conservation charity Plantlife has a well established common plants survey that anyone can contribute to – take a look, at http://www.plantlife.org.uk/uk/plantlife-get-involved-common-plants-survey.html

Now is the perfect time to get involved.