Harebell Carpenter Bees

Our native bees come in all shapes and sizes – from the uvuncular bumble bees to the sporty leafcutters and the tricksy nomads. One of my favourites is also one of the most inconspicuous – you may well have seen them around a garden campanula, mistaken them for small flies and thought no further. Whilst I’m not advocating flies as worthy of oversight, the harebell carpenter bee (Chelostoma campanularum) is certainly rewarding if you take the time to look a little closer.

Harebell Carpenter Bee - Chelostoma campanularum

These tiny black bees are just 6-7mm long and black all over. The females have a white scopa – as illustrated in this BWARS profile of the bees – and the males are very similar in size and appearance.

We have a number of campanula species which are native to the UK, including the harebell along with a range of bellflower species which are larger and more akin to the ornamental garden varieties, such as nettle-leaved bellflower. Fortunately, these little harebell carpenters don’t seem too fussy and I’ve watched them on two different ornamental cultivars in our garden over the past few years.

To watch these bees around the flowers, you might be forgiven for wondering what precisely they’re doing – they often look for all the world as though they love the flowers… but don’t know what to do about it. In fact, they are intimately intertwined with the genus – the females will only collect pollen from bellflowers and this blog from Urban Pollinators has some great images of their specialised means of collecting this. They also mate in the flowers and females will wait for males in the flowers, whilst the males will  swarm and circle around on the hunt for females! Males will often shelter in the flowers in dull weather too.

These bees are aerial nesters – this means that they will seek out opportunities such as dry stems and holes in wood to nest in. This makes providing for this species in your garden very straightforward – simply plant some campanulas (the native harebell is a delightful addition to any garden) and provide some bundles of reed or straw at height for them to nest in.

The bee is on the wing from June through to August and has a mostly southerly distribution in the UK but certainly occurs around Grantham in the midlands!

Below is a slow-motion video of the harebell carpenter bees in our garden flying around an ornamental bellflower – but if you want to see some excellent images of the bees at rest, check out Ed Phillips’ blog post here. And if you want the detailed image of males and females, as well as habitat shots, head over to Steven Falk’s flickr albums!

Harebell Carpenter Bee - Chelostoma campanularum

How to make a bee hotel

If you look carefully at who’s visiting your flowers in the spring and summer, you’ll soon spot a range of subtly different and equally beautiful bees alongside the industrious honeybees and the avuncular bumblebees. We have 250 species of ‘solitary bees’ in the UK – far more than the social species combined and a number of these can be encouraged to nest in your garden through provision of pollen, nectar and a place to stay!

Who can you expect to see?

A number of different species can be found using bee hotels. One of the most common, and most widely provided for, is the red mason bee. These rusty coloured bees, around the size of a honey bee, are on the wing from March to July and will readily take up residence in a well constructed bee hotel. The females visit ‘mud mines’ where they gather up balls of soft mud to line and seal the individual cells within the nest tubes. They are a welcome visitor to any garden, especially if you have fruit trees, as they are a prolific pollinator, estimated to be over a hundred times more efficent than the honey bee. A number of the other Osmia (mason bee) species are also likely to pay a visit if the conditions are right.

The photograph below shows a red mason bee feeding on green alkanet – a great source of early-season nectar for spring bees.

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As the year progresses, leafcutter bees emerge in the summer. These are so named for their habit of cutting circles of leaf from species such as roses which they use in a similar way to the mason bees – to line their nests and segregate the cells. A good garden can provide the leaves they need to line their nests; the nest tubes themselves; and a good source of pollen and nectar for the adult bees to feed on.

The photograph below shows a brown-footed leafcutter – Megachile versicolor – visiting our bee hotel last year with a section of leaf ready to line its nest.

Orange-vented leafcutter bee building its nest with rose leaf segments in our home-made Bee Hotel

Alongside the charismatic species such as bees, you might also get some less charming but equally intriguing species. Last year, one of the nest tubes in our bee hotel was used by a willow mason wasp who hunted and paralysed beetle larvae to bring back to its nest.

But a word of warning: don’t expect the hotel to be free of uninvited guests. The life history of bees is a complex one – they have ‘enemies’ including other bees (often named cuckoo bees), flies and wasps which will parasitise and exploit them. This is all part of the ecosystem which has developed and whilst you might feel protective towards your bees, you should bear in mind that the parasitic species is generally rarer than its prey!

The photograph below shows a wasp using its long ovipositor to inject its eggs into the nest tube of one of the solitary bees in our garden bee hotel.

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How to make a bee hotel

It’s worth bearing in mind before you begin, just what you are aiming to do in creating a bee hotel. The species who are most likely to be attracted to the hotel are those which nest in cavities naturally; these include dead plant stems, holes in decaying wood often bored by beetles, and holes in brickwork. What you are seeking to do is replicate and ideally perfect these conditions for your garden visitors.

Whilst there are many purpose-built boxes on the market these days, the nesting opportunities are easy to make yourself and understanding what you are tying to achieve can open up lots of opportunities to be creative. You could create the features within existing woodwork in your garden, say a fence post in a sunny spot or an old sleeper. Similarly you could create several small hotels of just the right size and shape to fit in with your existing materials in different locations around the garden. The additional advantage of multiple small hotels is that you are avoiding a dense congregation of nests, which may be more susceptible to parasites and ‘enemies’ and thereby maximise the chances of your bees successfully rearing broods.

Firstly: the materials.

You can use lots of different materials, but do remember that wood treated with chemicals may be harmful to bees so certainly avoid anything freshly treated. Offcuts of old wood can be good though, along with logs, bamboo canes and other similar materials. You need your materials to be a minimum of around 8 inches deep, but some variation can be fine.

Secondly: the structure.

We have had bees happily nesting in holes in fence posts where old screws have come out, but if you are making a bee hotel from scratch, you should aim to ward off any potential hazards. Aim to make your structure rain-proof – this often means constructing a simple box within which to place the nest tubes and put on a sloping roof which overlaps the top. This will allow the rain to drain off and keep the nest tubes dry. A box also helps to hold your tubes together and give them stability. I used a back board as well, which could be used to affix the different blocks of wood and keep the whole thing stable.

Thirdly: the nest tubes

One way to achieve the nest tubes is to use a drill and create various sized holes in the pieces of wood. These should be up-to 7 inches deep and vary in size between 2mm and 10mm. Different bee species like different sizes of holes, and producing a variety will maximise the chances of the hotel being used by a number of species. Larger holes, around 8mm, seem to be favoured by the leafcutter bees with smaller holes used by smaller mason bees and species such as the delightful harebell carpenter bee. It’s important to make the entrances to the holes smooth, by sanding or otherwise removing rough wood and splinters asd these could damage the wings of the bees.

Another option is to use bamboo canes cut to the correct lengths – again taking care to avoid splintered edges. A variety of different sizes will similarly work for a range of species.

Dead plant stems, especially those robust enough to maintain their structure such as hogweed, reed or nettle, can provide a ‘natural’ nest tube. These can be bundled together length-ways to create a tempting array of opportunities.

With the box illustrated below, I opted for a combination of all of these materials which creates a pleasing arrangement – an important consideration if you are going to site this somewhere prominantly in your garden – as well as providing a diverse range of nesting opportunities.

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Fourthly – the position

The bee hotel should be placed somewhere south facing, in full sun if possible. The key requirement is sun in the morning to allow the bees to warm up and start their day – like all invertebrates, they are cold blooded. You should also ensure that they are not shaded too much by vegetation, for the same reason.

The video below is a selectively-speeded clip, taken over 15 minutes in realtime, of bees emerging tentatively as the sun warms the bee hotel in the morning.

Finally – the management

Whilst you can fit and forget, many will advocate that an element of management is in the best interests of the bees to secure the long-term value of the bee hotel. Whilst parasites and enemies are a natural part of the bee’s life history, the creation of durable, artificial nesting habitat with higher densities of nests than would occur naturally can affect the balance of parasite and host and result in the bees failing to successfully hatch out a new generation.

I am no expert in this area and will defer to others for this advice. This website is a great resource for further and more detailed reading on how to make a bee hotel, and how to manage it. Some sources talk of bees vs. pests when discussing management and this is, to my mind, an unhelpful distinction. Where your provision of nest boxes is not significantly upsetting the balance between the bees and their parasites/predators, then the loss of some eggs and indeed some broods to species of parasitic wasp and flies which depend upon them for their own survival is entirely to be expected. A wild garden should have space for these as well as the bees – creating a habitat invites an ecosystem rather than a species in isolation. However creating a ‘sink’ for bees which are drawn to the nest box and then fail to raise a brood because of the density of paratises or the impacts of fungal attacks is not a desirable outcome. In this instance, the bees may have been better served by not creating the bee hotel in the first place. Cleaning out holes in wood; swapping bamboo tubes; and replacing dead stems is recommended by some, but you need to be careful in your timings and approach to ensure that your actions are not inadvertantly removing the eggs and larvae before they hatched.

One obvious way to minimise some of the risks would be the creation of multiple, small bee hotels around your garden if possible, as this addresses many of the density issues and reduces the risk of entire broods failing in a given year!

Find out more…

For more information about solitary bees – Ryan Clark has put together an excellent introduction to the species native to the UK in this Wildlife Trusts article. If you’re looking to identify solitary bees in your garden, this is a great place to start. If you begin to delve deeper, it won’t be long before you reach the work of Steve Falk who has produced the Field Guide to the Bees of Great Britain and Ireland – an indispensible book if you are looking to further your knowledge of our native species.

2017 in Bees

If trees are the elders of the countryside, then the bees are part of the summer pageantry of a fairground, here in numbers for just six months of the year they work hard and play hard, getting drunk on nectar whilst setting themselves up for the long winter ahead.

I love to look back on photos from the year and see the changes in light and colour as well as species – hopefully this will come across in the retrospective below:

Honey bee – Apies mellifera

The first bees of the year for me, appeared on valentines day a whole month before I saw the next. These were the honey bees on the gorse flowers, just a stones throw from the edge of the residential in Grantham. I would expect these were from a hive somewhere in a garden nearby. The footpath here winds through the gorse shrubs, creating a sheltered microclimate filled with the coconut-scent of the flowers making an ideal first-forage of the season!

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Early Mining Bee – Andrena haemmorhora (male)

This beautiful little bee is the first mining bee I saw in 2017. This was taken at Farndon Willow Holt – a Nottinghamshire Wildlife Trust reserve which is best known for its collection of willows but with many other habitats besides. This little male mining bee was on a blackthorn flower against the blue spring sky in March.

Early bumblebee – Bombus pratorum

This is the aptly named ‘early’ bumblebee – visiting winter-flowering honeysuckle in my parents’ garden back in March. Ornamental and garden plants such as this can really extend the range of nectar sources available for early-flying bumbleebee queens in the springtime.

Ashy mining bee – Andrena cineraria

This little bee appeared on the inside of our new greenhouse as we were assembling it over easter. The structure was only half-glazed at this point and upon flying in, it must have flown upwards and become trapped in the glass roof. After a few photos, I sent it on its way! These grey and black mining bees are very striking, and often the first ‘unusual’ bees which people notice in their gardens before discovering the world of different bees which their flowers support.

Early Mining Bee – Andrena haemmorhoa (female)

This was one of the first mining bees I ever took real notice of – it was searching for its hole next to me in the garden and I was struck my the beautiful patterning of the fur. This shot was taken in a spot I came to think of as ‘bee alley’ – just around the corner from work it has a good patch of green alkanet – an early flowering member of the forget-me-not family – and the aspect catches the sun at lunchtime resulting in a new species pretty much every day I visited! Read more about the bees I saw there on this page.

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Bumblebees along The Drift

The Drift is an ancient track which runs along the Lincolnshire/Leicestershire county boundary near us. The limestone grassland is filled with wildflowers but the key species for bumblebees is always the viper’s bugloss – it produces nectar-rich flowers which are accessible to a range of the ‘generalist’ bumblebees and will keep on producing more week after week. If you want to boost the bee-value of your garden – this would be my top tip!

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Tree Bumblebees (Bombus hypnorum) Mating

The house next door to us had a tree bumblebee nest this year and one day, the garden was filled with the tandem flights of newly emerged queens and sharp-eyed males who had latched on to mate with them. It was amazing to watch the queens successfully take off with such an extra weight on their backs! You can see in this photograph how much smaller the male bumblebees are compared with the queens.

Tree Bumblebee (Bombus hypnorum) Nest

This was a photo of a tree bumblebee arriving into its nest in a fallen willow. The nest was in a failed hazard beam meaning the cavity opened on both sides with the nest situated in the cavity above. By positioning myself on the opposite side, I managed to get this shot of a worker approaching and about to enter the nest.

Tree bumblebee entering its willow-cavity nest

Black Ruderal Bumblebee – Bombus ruderatus

This was another photograph taken along The Drift – this time of a bumblebee which had spent the night on a knapweed flower and had not yet warmed and woken up. This was one of several individuals which were all black – a melanic version of the ruderal bumblebee which is typically banded. This species of bumblebee is thought to be on the increase – possible reasons could include climate change or the increased planting of red clover.

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Leafcutter Bee (Megachile versicolor)

I had made a bee hotel way back in April and this was my favourite resident – a leafcutter bee (probably brown-footed leafcutter) which would spend its days bringing sections of leaf back to seal up egg cells within its nest tubes.

Orange-vented leafcutter bee building its nest with rose leaf segments in our home-made Bee Hotel

Male Bumblebee (species… forgotten!)

This photo was taken after a summer rain shower – this male bumblebee had been caught out on the verbena in the garden and was waiting to dry out. You can see the characteristic ‘yellow moustache’ which typically is found on the males of the commoner species including Bombus lucorum, B. lapidarius, B. pascuorum, B. jonellus and B. praetorum

Carder Bumblebee (Bombus pascuorum) on Carline Thistle

I liked the colour scheme of this shot – the carline thistle (in full flower despite the appearances!) and the carder bumblebee share the same straw-coloured brown which seemed characteristic of the countryside in late summer. This photograph was taken at Harbury Spoil Banks – a Warwickshire Wildlife Trust reserve.

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Solitary Bee on creeping thistle

I’m afraid my ID skills aren’t up to this one, but this is one of the small solitary species resting in August. I like the way the thistle flower looks similar to an anemone, reminding me of the clown fish and sea anemone relationship. This little bee was actually blowing bubbles into the wind when I found it – a behaviour thought to be useful in reducing the water content of the nectar and increasing its concentration.

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Heath bumblebee – Bombus jonellus

This was a male heath bumblebee on the heather at Curbar Edge taken just before sunset. This was one of the last bees I saw in 2017, and the first time I have seen this species which is common in heathland areas but can also be found in parks and gardens near to the habitats. I liked the way this one posed at the top of the strand – actually he was trying to be lazy and reach the next flower without taking to the wing!

Bee is for beginnings…

It is incredible what you find, when you start to look. There is a certain sloe which grows along the River Witham in Grantham, and for some reason it seems to beat every other blackthorn to bloom. I was walking along in March and saw a bumblebee visiting the flowers. It turned out to be a tree bumblebee – the first species I could name beyond ‘bumble’. Throughout the summer, I have added new bumblebees to my acquaintance as well as many other characters which together make up the family bee. I have very much more to learn and look forward to doing for many years to come, but I was amazed at just how much I have never noticed before. I have gone all these years and yet never seen mining bees visiting the garden, or the nomad bees lurking near their nests. I have never watched mason bees collecting mud or realised that they have their tunnels in the walls of our house. Tiny, beautiful solitary bees and huge queen bumblebees, leafcutters and honey bees and that’s before we even get on to all the pretenders; the hoverflies and beeflies which imitate and exploit! I have illustrated below just a few of those I have been lucky enough to see this year, I hope it might inspire you to explore for yourself.

Bumblebees

Early in the year, the queens emerge from hibernation and feast on the early flowering plants; the heathers and hellebores were a favourite in the garden whilst long-season gorse flowers are an ideal early-spring feed in the wild. These queens will establish nests and then the whole process of ID becomes more complicated as the workers and males appear – similar but subtly different to the queens of the species. There are 24 species in the UK but around six are the most commonly encountered; the Bumblebee Conservation website is a fantastic resource to get you started and with a few key ID tips, you are well on your way with most species!

The first bumblebee I tried to ID - the tree bumblebee (Bombus hypnorum)
The first bumblebee I tried to ID – the tree bumblebee (Bombus hypnorum)
A queen garden bumblebee (Bombus hortorum)
A queen garden bumblebee (Bombus hortorum)

Mining bees

These bees are so named because they dig holes in the ground in which to lay their eggs. There are around 100 species in the UK and they include some exquisitely beautiful specimens such as the tawny mining bee which is a stunning shade of autumnal red. The ashy mining bee and early mining bee also paid a visit to my garden this year. In contrast to the bumblebees, they are largely solitary although some species do nest communally.

A tawny mining bee (Andrena fulva) photographed along the Grantham Canal
A tawny mining bee (Andrena fulva) photographed along the Grantham Canal
An early mining bee (Andrena haemorrhoa) photographed in my garden
An early mining bee (Andrena haemorrhoa) photographed in my garden
An ashy mining bee (Andrena cineria) visiting a hogweed flower along Grantham Canal
An ashy mining bee (Andrena cineria) visiting a hogweed flower along Grantham Canal

Nomad bees

These small bees are not immediately obvious to identify as such on first glance – they are rather more wasp-like than bee-like. There are around 30 different species and they parasitise the nests of other bees – especially mining bees – laying their eggs in the nests which gives rise to the alternative name of ‘cuckoo bee’. There are also cuckoo bumblebees which behave in a similar manner with the nests of bumblebees although I have not (yet) managed to spot one of these.

A nomad bee on gorse flowers at the Hills and Hollows in Grantham
A nomad bee on gorse flowers at the Hills and Hollows in Grantham

Mason bees

There are several species of mason bees in the UK – these are so called because they use mud when constructing their nest. We have red mason bees nesting in holes in the pointing of our house but many different crevices and cavities can be used. The bees lay their eggs inside the tube structures and then seal the end with mud. I came across a ‘mud mine’ down beside the River Witham in Grantham where mason bees were coming and going collecting mud, with up to 10 present at any time. The hollows you can see in the photograph were excavated by these bees which gather up the mud and fly back to their nesting sites with it clutched between their mandibles.

A red mason bee (Osmia rufa) gathering mud from the bank of the River Witham in Grantham
A red mason bee (Osmia rufa) gathering mud from the bank of the River Witham in Grantham

Leafcutter Bees

These bees have a similar ecology to the mason bees, only they use leaves instead of mud as their medium of choice when sealing up their entrances. I spotted this one in our back garden but was lucky enough to watch one ferrying segments of rose leaf from a nearby bush to a bee-hotel in my parents garden. The semi-circular cuts around the edge of the leaf are quite distinctive when you’ve seen them once and a sure sign that these bees are around.

A leafcutter bee resting on a plantpot in my back garden
A leafcutter bee resting on a plantpot in my back garden

Solitary bees

There are a large number of small solitary bees which are often difficult to identify as they are so small and subtly different. This one was identified for me as a male Lasioglossum calceatum, probably the commonest of this particular genus in the UK.

A male Lasioglossum calceatum solitary bee on a burdock flower - distance is relative!
A male Lasioglossum calceatum solitary bee on a burdock flower – distance is relative!

Honey bees

There is only one honey bee species in the UK and it is quite distinct from the rest. Whilst the patterns may vary, the shape and general demeanor make them quite distinctive. Many honey bees belong to hives but wild populations also exist and you can see them from the first spring sunshine through to the last throes of summer.

Honey bee (Apis mellifera) leaving a Himalayan balsam flower
Honey bee (Apis mellifera) leaving a Himalayan balsam flower

The active season for many invertebrates, including the bees, is coming to an end. Common carder bumblebees are still around in good numbers but it won’t be long until they too vanish from the flowers. I am already looking forward to next spring when the queens emerge from their hibernation and there will be a new host of commonplace marvels to notice for the first time. The sheer diversity is breathtaking – it only requires you to bend a little closer to the ground to take it in. I would cordially invite you to do so!

Common carder bumblebee (Bombus pascuorum) feeding at a fumitory flower
Common carder bumblebee (Bombus pascuorum) feeding at a fumitory flower