Tag Archives: common carder bee

The week the Swifts departed

It’s become something of a ritual.  Each year in the first week of August, we scan the sky nervously.  We’re looking for birds but anticipating an absence.  It’s not that we want the swifts to go but we know they must.  The next part of their life is lived in Africa where they spend the months of September to April after their long migration.   When they leave us, it’s a sign that the year has moved on and summer is gradually giving way to autumn.

This year the swifts arrived at the beginning of May.  We had been watching out for them for several days and then finally we noticed a few birds swooping around in the sky above our house.  With that dark crossbow silhouette and those rapid bursts of wing beats interspersed with smooth glides, we were relieved and pleased to see that the swifts had returned.  Messages circulated on our local WhatsApp group celebrating their arrival and it was clear that our neighbours were just as interested as us.  Gradually their numbers built up as more birds arrived from Africa.  Numbers varied and, on some days, we saw none but at their peak this year up to 30 swifts were swooping and screaming across the valley below our house.  The valley contains a community garden with flowers and trees and most likely the swifts come to feed on the insects that breed there. 

Throughout late spring and summer we watched them flying backwards and forwards at high speed, changing direction as they banked and turned, sometimes going into steep dives pulling out at what seemed like the last minute, screaming as they went.  Sometimes a group flew about together, individual birds adjusting their relative positions before splitting into smaller groups like rockets at a firework display.  Sometimes the birds flew towards our terrace of houses, turning finally to avoid the brickwork or deftly navigating the gap between this and the next terrace.

Swifts near our house

The position of our house gave us a very privileged view of the birds.  It is one of a terrace of five houses built on a ridge on the southern edge of Totnes overlooking the valley and community garden so that our kitchen window is level with the tops of the trees below.  Sometimes, when the birds were flying about near the houses, they passed at speed very close to our kitchen window giving us views worthy of a nature documentary programme.  Sometimes, when we sat outside on the patio, the birds passed directly overhead screaming as they went, a joyous and very visceral experience.   

Swifts over Totnes seen from our kitchen window in 2020

Sitting outside, we could also see some of the birds swooping up to the eaves of two houses in adjacent terraces where they made nests.  They also nested in the roof space of one of the houses in this terrace and, for the first time, they occupied a wooden bird box fixed near the eaves on another house.  The box was put up several years ago by a neighbour.   It was occupied by sparrows one year and tree bumblebees in another but this year the swifts used it.  Swifts tend to return to the same places to nest each year so we have high hopes of seeing them in this box in the future. 

The second week of August arrived and the birds were still about.  Although we expected them to go any day, they still had the ability to surprise.   On the 10th just before 9 o’clock with the sun setting, I was standing outside looking across the valley, watching the light fade and the colours changing.  I hadn’t seen swifts that day and wondered if they had left.  The western sky was still bright, a luminous pale blue, and light cloud in the northern sky gathered pinkish-orange tinges from the setting sun.  Suddenly, above the general hum of human activity I heard the familiar screaming sound announcing the arrival of a volley of swifts.  About ten birds in groups of two or three were heading straight towards me just above head height.  At the last minute, though, they changed course to fly through the gap between the terraces. 

If all this wasn’t exciting enough, I had a second fascinating close encounter with the non-human world in the same week, this time with a very different species and some distance away from Totnes.

The second story began when, in the first week of August, Tim Worfolk, a local bird illustrator and naturalist, reported on social media that he had seen some rare and unusual bees on a nature reserve south of Exeter.  This was the first report of this species in Devon and I couldn’t resist the opportunity to go to have a look.  So, on August 9th I made the 40-minute drive to the Exminster Marshes, part of the river Exe floodplain and a wetland nature reserve managed by the RSPB.   I had driven through a shower on my way over and rain threatened later but it was my only free day that week.    I parked in the reserve car park and made my way down a lane towards the Exeter Canal and the river Exe.  Signs of water were never far away.  Although the lane was enclosed by hawthorn bushes and other scrub, reeds grew through the vegetation and a ditch half full of water ran alongside the lane.  Late summer flowers grew in the hedges including bright yellow fleabane, the lemon-yellow snap dragon-like flowers of common toadflax and the pink cushions of hemp agrimony. 

The Exminster Marshes showing the flat watery landscape

I left the lane to cross open grassland criss-crossed by ditches with rough stony bridges.  Clumps of tussocky grass grew across the marshy land along with stands of creeping thistle that attracted small copper and small tortoiseshell butterflies and some chunky hoverflies.  Cows grazed nearby and this would have been a peaceful spot had it not been for the M5 motorway bridge crossing the marshes towards the north creating a continuous background hum of traffic noise.

At the end of the field path, I crossed the cycle track and scrambled up to the towpath at the edge of the Exeter Canal.  The pleasant town of Topsham with its Dutch-gabled buildings lay across the river Exe on the far side of the canal.  The towpath was quiet, most likely because of the weather, but a few walkers passed and two stand-up paddleboarders drifted lazily past on the canal. A little drizzle was now falling and I began to wonder if any bees would be about but I decided to press on.  Banks of reeds lined the towpath and flowers grew up through the vegetation.   I noticed the pink flowers of marsh woundwort with their intricately decorated lip and a few tall spikes of purple loosestrife.  Then, as I walked southward, thick clumps of yellow flowers appeared in the canal-side greenery.  This was yellow loosestrife, a plant that grows in wet places and, with its copious sprays of bright yellow cup-shaped flowers produced in late summer, it shone like a beacon of light on this gloomy day.   Each flower contained large amounts of grainy yellow pollen and the plant grew in many places along the canal up to the lock where the canal and river merge. (The picture at the top of this post shows some the yellow loosestrife flowers)

Vegetation by the side of the Exeter Canal showing yellow loosestrife and marsh woundwort. Topsham is in the background.

Light drizzle continued to fall and I had almost given up on finding bees when I spotted a medium-sized dark insect in one of the yellow loosestrife flowers.  Visually, I couldn’t see much to distinguish this insect except some white hairs on the hind legs. Photographs also showed the prominent white hairs on the back legs along with some black as well.  These characteristics together with the association of the insect with the yellow loosestrife flowers showed that this was a female Macropis europaea, the yellow loosestrife bee, one of the bees I had come to find.  The photographs also showed a few small drops of rain on the insect which was sheltering on this damp day and essentially immobile, making it easier for me to take pictures.  Further along the canal, I came across another dark insect also resting in a yellow flower and in this case, photos revealed its swollen hind legs and its prominent yellow face, characteristic of a male of the same species. 

Female Macropis europaea showing the white and black hairs on her hind legs. Look out for the raindrops.
Male Macropis europaea showing his swollen back legs
Male Macropis europaea showing his yellow face and swollen back legs

These are the bees reported by Tim Worfolk but why was I so interested in seeing them?  They are rare which is of course one reason. They also have some very unusual characteristics being the only UK species of bee that collects floral oils and they find these oils in the flowers of yellow loosestrife.   

Within the flowers there are tiny glands that secrete floral oils.  The glands, termed trichome elaiosomes, are found towards the lower part of the inside surface of the petals and along the stamen tubes and the oils collect near the glands.  The female Macropis bees have specialised brushes of hair on their front and middle legs that they use to collect these oils which are then transferred to the hairs on their back legs, sometimes mixed with pollen also collected from the flowers.  The female bees use the oils for two purposes, to waterproof the inside of the nest chambers they construct in wet places and, mixed with pollen, to provide food for their larvae. 

When I visited, the damp conditions prevented the females from flying so I was unable to observe them collecting pollen or oils.  Local naturalist John Walters has a nice video of the female bees collecting pollen where the bees look like they are wearing bright yellow pollen pantaloons.

I was glad to have made the trip to Exminster Marshes, despite my doubts about the weather.  Seeing these oil-collecting bees and understanding the close and reciprocal relationship they have with the yellow loosestrife flowers was an unexpected gift.   

But what about the swifts?  August 13th was the last day we saw the birds near our house so we assume they are now on their long migratory journey.  Their presence has not only entertained us but has enriched our lives this year, bringing us closer to the non-human world.  It has been an excellent year for the birds in terms of numbers and it was good to see them reproducing so well, especially in this time of environmental crisis. 

Marsh woundwort with common carder bumblebee (Bombus pascuorum)
Small copper butterfly (Lycaena phlaeas)
Hoverfly (Helophilus trivittatus)

An otter in a tree? – Lockdown Nature Walks 16

With Lockdown easing in the UK, this is the last Lockdown Nature Walk of this series.  I wanted to see how spring was progressing along a typical Devon country lane. So, on a mild day with intermittent sunshine and a light wind, I walked up Harper’s Hill on the western side of Totnes (as in Lockdown Nature Walk 7) to reach Jackman’s Lane and the ridgeway road.  It was an interesting walk but not always in the way I had anticipated.   After the account of my walk, I have included a relevant poem, “The Trees” by Philip Larkin

The prominent sign at the start of Jackman’s Lane proclaimed “Unmetalled Road” and the hard-packed, rutted, reddish soil base of the track showed evidence of regular use by farm vehicles and horses.  I made slow progress along the lane, examining the soil banks lining the track, occasionally pausing to enjoy the views across rolling countryside with fields and trees.  Skylarks sang their endlessly inventive songs overhead, plump queen bumblebees buzzed along the hedges and the wind carried the sound of a tractor.  Spring flowers decorated the soil banks including primroses, celandine, violets and stitchwort.  Nettles grew in a profusion of green together with thuggish hogweed leaves while the heavily flailed woody stems along the hedge tops were only just shooting.    

Then on a narrow ledge surrounded and almost hidden by grasses, my attention was captured by a flash of a different green, a silvery green.  When I looked carefully, I saw a fine lizard curled up neatly and basking in a shaft of warm sunshine (see picture at the head of this post).  The reptile was about 12cm long, a common lizard (Zootoca vivipara) with a complex pattern of black swirls and dots along its body.   The colours of common lizards vary and local expert, John Walters told me that the green colour probably helps the creature to avoid predators in this grassy environment. 

As I watched the lizard, I saw it eyeing me warily, so I left it in peace and carried on down the lane.  Butterflies occasionally surprised me by erupting from the track where they had been basking, rising too quickly to identify.  Then two of these insects materialised above me, dancing in the air, turning circles around each other before one fell to the ground just behind the left-hand bank.  I scrambled up and recognised it as a small tortoiseshell (Aglais urticae) with its brilliant orange, yellow and black markings.  It seemed to be fluttering its wings repeatedly as it danced above some young nettle leaves.  Was this a form of courtship behaviour? 

I continued to see or hear bumblebees as I walked and then towards the end of the lane, hoverflies began to appear.  Some were flying about but most were quietly basking on exposed leaves in the sunshine.  The hoverflies that I saw that day were all of the same species, the tapered drone fly (Eristalis pertinax), a mixture of males and females.   The more I look at hoverflies, the more I appreciate the beauty of these creatures and I hope the photos posted below show this.  Look, for example, at their wings which resemble panes of crazed glass and the neat bands of hair decorating their thorax and abdomen.

As I was watching the hoverflies, I heard a familiar but not entirely welcome sound.  Turning to look back down the lane, I glimpsed a galloping horse and rider approaching at speed.  I moved to the edge of the track to make way but the horse slowed down and walked past me.  I thanked the rider but she said nothing.  I may have spoiled her planned gallop along this unpaved country track!

Jackman’s Lane ended and I turned right along the ridgeway road in the direction of Totnes.  Views to the north across the valley below were hazy and Dartmoor lay invisible in the mist that enveloped the distant hills.  A farmer was treating the nearby fields with chemical fertiliser while ploughing the upper surface of the red Devon soil.  A plume of dust accompanied his tractor, so I walked on quickly. 

The ridgeway road runs roughly eastward so that the soil bank on one side is south facing, getting the benefit of the sun when it shines and encouraging growth.  Many flowers will appear here later in spring and even that day, I saw more here than along Jackman’s Lane including three members of the dead-nettle family. 

White dead-nettle was one of these with its hooded, slightly hairy flowers spreading splashes of snowy white among the lush greenery covering the bank.  A few red dead-nettle flowers had just pushed through the grasses and there were drifts of yellow archangel, a member of the family that has the look of a yellow dead-nettle.  Two kinds of yellow archangel grew on the soil bank, the wild flower with its all-green leaves and the garden throw out (argentatum) with silvery green leaves.  The garden variety blooms earlier and spreads more aggressively than its wild counterpart and it had formed a large yellow mat along one edge of the ridgeway road. 

The flowers of members of the dead-nettle family are similar with a wide lower lip like a landing pad to attract pollinators, sometimes marked with abstract patterns.  Above the lip is a hood concealing stamens that close over the inquisitive insect so that, when it leaves, it takes away some pollen to fertilise the next flower it visits.  Several common carder bee queens (Bombus pascuorum), some of the first I had seen this year, were taking advantage of the flowers.

While I was watching the bees, I became aware of a motor scooter that had slowed down and turned on the road behind me.  The scooter drew up at my side, stopped and the rider, an older man, swathed in coats and a large crash helmet, asked:

“Are you going towards Bowden?”

I thought he wanted directions and replied “Sort of”.

“Have you seen the otter in the tree?” he asked.

“What! An otter in a tree, it must be dead?” I replied in surprise.

“No, no”, he must have thought I was stupid, “it’s part of the tree, its uncanny how it looks like an otter, I am surprised more fuss hasn’t been made about it”.

He told me in some detail how to find it and I agreed to look.  

As he was getting ready to go, he looked at me oddly and asked “What’s a farmer’s favourite sport?”

“I have no idea. What is farmer’s favourite sport”, this was becoming surreal.

He revved up, looked fixedly at me again and, as he accelerated away, blurted out “fencing!”. 

I walked on and near the junction with the Ashprington road I could see the tree and the arboreal otter.  It was indeed an uncanny likeness. 

It was only then that I remembered it was April 1st but I haven’t made this story up, all this really did happen.

The otter in the tree

…………………………………..

“The Trees” by Philip Larkin

The trees are coming into leaf
Like something almost being said;
The recent buds relax and spread,
Their greenness is a kind of grief.

Is it that they are born again
And we grow old? No, they die too.
Their yearly trick of looking new
Is written down in rings of grain.

Yet still the unresting castles thresh
In fullgrown thickness every May.
Last year is dead, they seem to say,
Begin afresh, afresh, afresh.

…………………………………..

stitchwort
violet
small tortoiseshell butterfly on nettles
female hoverfly (eristalis pertinax), the eyes don’t meet in the middle of the head so this is a female
male hoverfly (eristalis pertinax), the eyes meet in the middle of the head so this is a male
white dead-nettle with common carder bee (Bombus pascuorum)
yellow archangel with common carder bee (Bombus pascuorum)

Seaside Storms and bumblebees

By the end of October, I had begun to feel that autumn was running away from me.   Then came the announcement that a second lockdown would be imposed.  So, one afternoon at the beginning of November, I decided I needed to get outside and went to Roundham Head in Paignton, one of my favourite nearby nature haunts.  Roundham Head sits roughly in the centre of the semi-circular arc of Torbay and from the southern side of the promontory there are fine long views around to Brixham with its harbour, small boats and breakwater. 

My main reason for visiting, though, was the public garden built on the southern slopes of the headland.  Here, zig zag paths meander up and down between borders stocked with tender and unusual plants many originating in warmer climates but thriving here in the mild maritime conditions of Torbay.  Many of these plants continue to flower here in autumn and winter.

I started at the top of the public garden looking south west with the low sun creating a dazzling mirror across the wet, low-tide sand at Goodrington where dogs and their owners rushed back and forth.  There was rain about, though, and across the bay Brixham was veiled in a grey mist, its landmark lighthouse barely visible.  Fortunately for my afternoon, the storm gradually moved away, and the cloud over Paignton evaporated leaving blue sky and sunshine but with a strong blustery wind. 

Agapanthus seed heads
Yucca gloriosa with its lantern shaped flowers

I wandered about the gardens where the low sun was casting long shadows from the trees and shrubs, draining them of colour, leaving dark silhouettes.   The agapanthus had lost their blue flowers, replacing them with mop heads of chunky green seed capsules, like so many large lozenges.  A fuchsia hedge, covered in blossom last time I visited was now nearly devoid of flowers but, in compensation, yellowish-brown clumps of fungi grew beneath.  Some plants were still in bloom, though, and I was surprised to find several large clusters of creamy coloured lantern-shaped flowers with pinkish sepals, hanging like ornate chandeliers above thick clumps of spiky strap-shaped leaves.  These are yucca gloriosa, plants originating in the southern US although they seem to be very happy here.

Hoverfly (Eristalis tenax) on rosemary

Spread about the upper, sunnier parts of the garden, I also found several large banks of rosemary.  The plant grows prolifically here, covering long stretches of wall where it hangs like a pale blue curtain.  It begins to flower in late summer and continues through the winter providing important forage for insects; many of its locations here are also sheltered from the wind.   Despite recent heavy rain, the rosemary was covered in small, spiky, silvery-blue flowers and this is where I began to see pollinators.   A hoverfly, probably Eristalis tenax, the world’s most widespread hoverfly, was feeding and I managed a few photos despite its jumpiness.  Then I saw the first of several small bumblebees each with a furry, pale chestnut thorax and stripy abdomen.  They were nectaring from the rosemary, moving purposefully from flower to flower, taking away a dusting of pollen from the overarching stamens as they fed.  These were common carder bees (Bombus pascuorum) and as well as feeding they occasionally basked on the stones of the wall in the sunshine.  Sometimes, two or more were present on the same patch of rosemary and there was a little joshing between the insects.

I took as many photos as the carder bees would allow in the hope of being able to see their back legs as these are a key to establishing the gender. Where I was able to see the back legs, the insects were all males and Steven Falk kindly helped confirm my identification. These males must be late survivors from the second brood. The mated females will have settled down to hibernate and the males are left to live out their short lives.

Common carder bee (Bombus pascuorum) feeding from rosemary. If you look at the back leg, the tibia has a rounded end so this is a male. Steven Falk also pointed out the antennal segments which are bulging rather than cylindrical, another characteristic of the males of this species.
Common carder bee (Bombus pascuorum) feeding from rosemary. This is another male with a round ended tibia.

Buff-tailed bumblebee (Bombus terrestris) feeding from rosemary. This was a worker carryng pollen, (I have other out of focus photos showing the pollen)

I did see one smallish buff-tailed bumblebee (Bombus terrestris) collecting pollen, a worker which most likely comes from one of the winter active colonies that live in these gardens.  I was surprised to see so few but perhaps the weather had put them off or there were other flowers available in the many nearby private gardens.   The surviving male common carder bees have no nest to return to for shelter which may be why they were still foraging in this threateningly damp weather.

The storm over Broadsands and the change in the light

By now, another storm had bubbled up from the south west but this time it was closer and a fine grey haze hung over the beach and countryside at Broadsands just along from Goodrington.   The blustery wind chased the autumn leaves about and hurled a few large drops of rain at me, stinging my face.  The sea took on a sinister greenish blue tone and a kestrel appeared, hovering in the wind above the gardens, eventually landing on the steep cliff face.   I decided to get back to the car before the rain set in properly. 

500 dead bumblebees – the chemical blitz of modern farming

In September I wrote about the mysterious death of 500 bumblebees. New information has emerged about this incident so I have rewritten the post:

Earlier this year, Sheila Horne was walking at Hacton Parkway, a public park and conservation area in Havering, East London. April is normally a good time to see insects in their prime so she was very surprised to find many dead and dying bees near the path. She alerted local naturalist, Tony Gunton who identified the insects as bumblebee queens from three species, red-tailed, buff-tailed and common carder. This was not a minor incident, there were as many as 500 bees affected.

Chemical analysis of the dead bees

Natural England was appointed to investigate the insect deaths and samples of dead bees were sent to FERA in York for analysis. The results were released in August and showed that the bees were contaminated with the neonicotinoid insecticide imidacloprid and two fungicides, flusilazole and epoxiconazole. Imidacloprid can be very poisonous to bees and bumblebees are more susceptible to this chemical than honeybees. Imidacloprid is currently subject to a two year partial ban for some agricultural uses in the EU. Neither fungicide on its own is especially toxic to bees although flusilazole was phased out this October because of its high toxicity to fish and because of other potential toxic effects.

A nearby field of oil seed rape as the source of the chemicals?

The chemical analysis raises two questions. Where did the bumblebees pick up these chemicals? Were these chemicals responsible for the bee deaths?

Neither question can be answered definitively but as so many dying bees were found together in one place, it seems likely that the source of the poisoning was close by. Hacton Parkway lies alongside arable farmland and at the time of the poisoning some of the land was planted with flowering oil seed rape, so it is a reasonable conclusion that the bees had been feeding there. Because of the chemical analysis, it was initially assumed that the crop had been planted using seed treated with imidacloprid ahead of the ban and that the imidacloprid had killed the bees. Natural England have recently concluded their investigation and found that in fact the seed used to plant the crop had been treated with another neonicotinoid, thiamethoxam. Neither imidacloprid nor epoxiconazole had been used on the crop and the last spraying with flusilazole was in November 2013. Analysis of the dead bees for thiamethoxam failed to detect any of the chemical but this could have been due to losses before the analysis.

What killed the bees?

So, why did these bees die? Because there are so many unanswered questions we cannot be sure. The dead bees were contaminated with imidacloprid but the oil seed rape crop was not the source. We can only assume that the bees fed elsewhere on imidacloprid-treated crops and were flying with this chemical in their systems. It is known that at typical field concentrations, imidacloprid does not kill bumblebees.

There is also the question of how the bees were exposed to the two fungicides if the oil seed rape had not been sprayed with these chemicals during the flowering season. As with the imidacloprid, we have to assume that the bees were exposed elsewhere. It is possible that the fungicides weakened the bees or made them more susceptible to the neonicotinoids. There is some evidence for such interactions for other insecticide/fungicide pairings.

Because the bees died close to the treated crop, the focus of lethality has to be on the thiamethoxam, now known to have been used on the oil seed rape. Although thiamethoxam is indeed an insecticide, there is evidence from one lab-based study and another field study (albeit lacking controls) that, at field-realistic concentrations, thiamethoxam is not lethal to bumblebees. I find it unlikely, therefore, that thiamethoxam alone killed the bees, providing the farmer followed safety guidelines.

We shall never know what actually happened at Hacton Parkway but my best guess is that these bees were flying with the three chemicals in their system and encountered the thiamethoxam-treated oil seed rape. When they fed from it, they picked up the additional neonicotinoid. Two neonicotinoids, with perhaps synergistic effects of the fungicides, were too much and they died.

The investigation is now closed!

The investigation is now closed and it will be impossible to resolve the many questions raised by this incident, which is a pity. Despite this uncertainty, the results of the chemical analysis stand. These bees died with three chemicals in their bodies: one neonicotinoid and two fungicides. They were also exposed to a second neonicotinoid. This was no laboratory experiment; this reflects what is happening around us when these chemicals are used. Have a look at this report to see more evidence of the widespread use of chemicals in UK farming. Our agricultural practices have led to this chemical blitz and the result is the deaths of important pollinators. How often is this occurring on a lower level but not being noticed or reported?

I should like to thank Tony Gunton (local naturalist) and Helen Duggan (Press Officer, Health and Safety Executive) for sharing information about this incident.

500 dead bumblebees – pesticides leave their deadly trace

Earlier this year, Sheila Horne was walking at Hacton Parkway, a public park and conservation area in Havering, East London. April is normally a good time to see insects in their prime so she was very surprised to find many dead and dying bees near the path. She alerted local naturalist, Tony Gunton who identified the insects as bumblebee queens from three species, red-tailed, buff-tailed and common carder. This was not a minor incident, there were as many as 500 bees affected.

Natural England was appointed to investigate the insect deaths and samples of dead bees were sent to FERA in York for analysis. The results were released a few weeks ago and showed that the bees were contaminated with the neonicotinoid insecticide imidacloprid and two fungicides, flusilazole and epoxiconazole. Imidacloprid is very poisonous to bees with bumblebees being more susceptible to this chemical than honeybees. Imidacloprid is now subject to a two year partial ban for some agricultural uses. Neither fungicide on its own is especially toxic to bees although flusilazole is due to be phased out this October because of its high toxicity to fish and because of other potential toxic effects.

But where did the bumblebees pick up these chemicals? We cannot be sure but as so many dying bees were found together in one place, it seems likely that the source of the poisoning was close by. Hacton Parkway lies alongside arable farmland and at the time of the poisoning some of the land was planted with flowering oil seed rape, so it is a reasonable conclusion that the bees had been feeding there. It is thought that the crop had been sown in autumn 2013 using seed treated with imidacloprid, just ahead of the ban. According to John Rennie of Natural England there had been no spray applications of insecticides or fungicides since the beginning of 2014.

So, why did these bees die? Because there are so many unanswered questions we cannot be sure. The imidacloprid used on the oil seed rape has been blamed by some but I can’t see how this could be a problem if the farmer followed safety guidelines. There is good evidence that exposure to typical agricultural levels of imidacloprid does not kill bumblebees although there is also good evidence for sub-lethal effects on behaviour and reproduction. It is, however, becoming apparent that neonicotinoids such as imidacloprid accumulate in soil so perhaps exposure levels of the dead bees were higher than expected. Soil testing would be informative here.

There is also the question of how the bees were exposed to the two fungicides if no spraying was performed during the flowering season? Does this mean that these chemicals persist for long periods or has there been spraying elsewhere? Perhaps the fungicides weakened the bees or made them more susceptible to the imidacloprid. There is some evidence for such interactions for other insecticide/fungicide pairings.

Although the investigation continues, it may be quite difficult to resolve some of these questions. Despite this uncertainty, the results of the chemical analysis stand. These bees died with three chemicals in their bodies: one insecticide and two fungicides. This was no laboratory experiment; this reflects what is happening around us when these chemicals are used. Our agricultural practices have led to this and the result is the deaths of important pollinators. How often is this occurring on a lower level but not being noticed or reported?

With thanks to Tony Gunton for talking to me about this incident