Having bumblebees nesting in the garden is a great way to learn about them. If you have a nest, you may at first just see a single queen carrying food to the nest, which she stores for her future offspring. A few weeks later you should see the first worker bees who will be helping the nests get larger, and hopefully they’ll soon be followed by new queens or males, which should mate with males and queens from different nests before the new queens go into hibernation.

Providing nesting sites for bumblebees can be as simple as just leaving a quiet spot somewhere such as a corner or behind a shed, and letting the weeds and grass grow tall. But if you want to go further than that, you could try making a bumblebee nest space yourself. We have teamed with up with the people at Hartley Botanic to produce this guide for making bumblebee nests. It may seem strange to think about nesting bumblebees in late summer, but if you make one now you may find that mice will use it over the autumn and winter. Bumblebee queens searching for nests actually seek the scent of mice when looking for nests. Having the mice in residence now could increase your chances of having your very own bumblebee nest next year.

So go on and have a go, and let us know if you have made any successful bumblebee nests yourself!

What is a winter-active bumblebee?

Since the 1990s, naturalists have noticed that, rather than hibernating, some bumblebees have been active all winter. Queens and workers have been seen foraging for pollen and nectar from a wide range of winter-flowering plants, and mating pairs have been recorded in February. These have almost all been identified as the Buff-tailed bumblebee (Bombus terrestris) and it is clear that a proportion of queens produced over the summer have begun to establish nests in the autumn instead of going into hibernation.

The Trust are working closely with the national recording body BWARS (Bees, Wasps and Ants Recording Society) to understand more about this behaviour – which species are involved, what’s driving the change, and how are they managing it?

To help, if you see a bumblebee between the 1 November – 1 March, please record it at iRecord. Include as much detail as possible – we’re particularly interested in answering these questions:

• Which species are involved? The Buff-tailed bumblebee is by far the most common, but there are winter records of several other species, though these may just be early-emerging queens.
• Which castes are involved? Queens, workers and males all tell us different things about the state of the colony they have come from
• Where in Britain are bumblebees becoming winter-active? How far north and is this just an urban phenomenon?
• Are the bees collecting pollen from the flowers or just feeding on nectar (or both)?
• Which species of flowers are being visited?
• What weather conditions are best for the bees?

If you do see any winter-active bumblebees it is particularly useful to have a series of repeated observations (e.g. weekly or fortnightly visits in suitable conditions, or a series of observations under varied conditions). This lets us better understand the dynamics of winter-active populations and which weather conditions they can best forage in.

What do we know so far?

Traditionally, hibernating queen bumblebees in the UK would emerge in the spring (roughly March-May depending on species and weather conditions), and establish a nest (in some cases with a partial second generation). As summer fades to autumn, the old queen and all of the workers and males would die off, the new queens would enter hibernation, and from October onwards our skies would be bare of bumblebees.

In recent decades however, this has not always been the case. From the 1990s onwards, bumblebees have been recorded actively flying and foraging through the November-February period. Several species have been reported, although most have been queens in February and are likely to represent queens emerging early from hibernation. For the Buff-tailed bumblebee, however, queens and workers have been seen actively foraging from October right through to March, collecting pollen as well as nectar, and males (and mating pairs) have been seen in early spring. Occasionally, the nests themselves have even been found.

These nests are able to survive on the increasing amount of forage resources available throughout the winter (both non-native plantings such as Mahonia and longer flowering seasons of native plants such as White Dead-nettle). Key flower species seem to be Mahonia (several species and hybrids), Winter-flowering Heather Erica carnea, Winter Honeysuckle Lonicera x purpusii, and Strawberry Tree Arbutus unedo, but foraging has been recorded from a wide range of plant species over the course of the winter. In at least some cases these nests are able to produce new reproductive individuals in spring, so the production of winter colonies is not a dead loss to the population, although it is unclear whether enough colonies survive that

Many of the sightings are in towns and cities. This may be because these tend to remain warmer than the surrounding countryside through the Urban Heat Island effect; alternatively there may be more winter flowers in towns than in the countryside (some non-native species such as Mahonia are common in amenity plantings and in gardens but scarce in wilder areas). It may just be that there are more people in towns so more eyes to spot bumblebees!  There are some sightings in the wider countryside, especially along the coast in the south and south-west, but winter-active bumblebees have been recorded as far north as Edinburgh and Dundee.

Wherever you are there’s a chance of seeing a winter-active bumblebee – please do send in any sightings to iRecord.

A scientific article on winter activity and foraging rates of bumblebees was published in 2010 (Stelzer et al) and can be downloaded for free from the journal website. An update is in preparation.

Frequently asked winter bumblebee questions:

• I’ve found a stranded bumblebee in bad weather, how can I help it? 
• I’ve disturbed a hibernating bumblebee, what do I do? 

By Ron Rock, Bumblebee Conservation Trust Volunteer

Don’t worry, to the best of my knowledge we are not about to be invaded, at least not by a belligerent force. However, the forces of good are beginning to stir, nest hunting queen bumblebees are on the move, one of which was recently described to me as the size of a B52. If you own a patch of pulmonaria or early flowering comfrey keep an eye open for a small ginger bee with a distinctive high pitched buzz and whizzing flight for this will be a male hairy footed flower bee. This bee jealously guards his chosen flowers, only allowing females of the species to forage in his patch. This way the all black females gain a protected pollen and nectar resource and he gets to perform the function that male bees are designed for, all in all a rather neat arrangement!

Many more of our 240 plus species of solitary bees will soon be emerging including one of my very favourite creatures, Osmia bicornis, the red mason bee. Red mason bees are a univoltine (single brooded) spring flying solitary bee active from April to mid June and occasionally a little later. They are approachable and docile little bees which are not given to stinging and so are safe around children and pets. Like all bees it is only the females that carry a sting and it has been said that the only way a female red mason will sting you is if catch her and roll her between your fingers! Red mason bees are hugely beneficial to our gardens and crops as they are excellent pollinators of fruit trees, together with a wide range of wildflowers. A single female red mason bee can do the pollination work of 120 honeybees and may in the future be commercially reared to pollinate fruit orchards in the U.K.

Male red mason bees emerge around two weeks before the females. When the females emerge they are mated by the waiting males and immediately set to work establishing a nest. Red mason bees use mud to build a linear row of chambers that they provision with a mixture of pollen and nectar into which an egg is laid and the cell is then sealed and work begins on the next one. This method of feeding their offspring is known as mass provisioning, bumblebees and honeybees employ a technique called progressive feeding, where the larvae are fed by worker bees as they grow. It takes a female red mason bee between 1 -1.5 days to build and provision one cell. The eggs hatch after about a week and the resulting larvae eats the pollen and nectar in the cell.

After around 56 days the larvae spins a cocoon and remains in this state within the cocoon for a further 48 days before metamorphosis into an adult bee takes place. The bees then remain quiescent within their cocoons until emergence time the following spring. The sole function of male is to mate with as many females as possible, drink copious amounts of nectar and eat pollen (well, boys will be boys). The males die off after about 6 weeks and the last females are active until mid June when they too perish. No red mason bee ever lives to see its own offspring and the sight of tattered and sun bleached almost grey females is a sure sign that spring is handing over to summer.

In a completed nest, male (unfertilised) eggs are laid in the cells at the entrance (vestibular) end of the nest and these are the first to hatch out in the spring. The end cell is always left empty and sealed with a thicker wall of mud than used in cells containing the eggs. This is a form of protection from predators and other species of bees and wasps which might otherwise nest in the vestibular cell and make it impossible for the red masons to emerge from the nest, thus causing them to starve to death. The cocoons consist of two layers, an inner silky lining and a surprisingly tough outer layer. The cocoons are white when spun but soon revert to the familiar brown colour shown here. On hatching the bees secrete a substance that softens the outer layer of the cocoons to aid emergence.

Bee nesters (bee hotels)

These are some of my nesters at home, mason bees always look along edges for a nesting site, the linear edge in this case being provided by the hedge beyond.

Red mason bees are our most numerous osmia species and it is surprisingly easy to attract them into our gardens. All you need is a bee nester, I don’t like the term bee hotel as the name gives the impression of a short stay, when in truth the bees once established spend their whole life in and around these structures. They can be bought though I prefer to build my own as a lot of the commercially available ones are not too well made. The nesters are stocked with cardboard tubes and liners, bamboo or routed out wooden trays, 8mm is about right for red masons. Nesting cavities should be at least 160mm long. The boxes with the single holes are release chambers where cleaned and overwintered cocoons are placed each spring. I no longer use drilled out logs and I will expand on these last two statements later in the year.

‘The Red Storm’
The males emerge first, a trickle then a flood. They spend their days jostling and jousting outside the nesters and occasionally nipping off to refuel before rejoining the riot whilst waiting for the emergence of the females. They seem to know when this will be as the activity becomes even more frenetic! Once mated the females start their nesting activity collecting mud in their mandibles and pollen on the underside of the abdomen. The males fade away and the activity becomes more ordered and fascinating to watch. These bees work so hard and by the end of June you are hopefully left with lots of tubes neatly capped off with mud. So sit back and enjoy these lovely little bees, they are like a fine wine served with the main course of bumblebees. A little later in the year, afters are served a la leafcutter bees, but that is another story!

Bliss! You can spend hours watching these cracking little bees!
Part 2 will follow in September/October when I will let you see how I look after the bees over the wintertime.
If anyone has any questions please feel free to e-mail me at ronrock@phonecoop.coop

By Suzanne Rex, Conservation & Volunteer Assistant

I began working at the Bumblebee Conservation Trust in February 2016, answering a number of enquiries and helping out in the office. Starting this job with little knowledge about bumblebees and other pollinators, I have been required to research a great deal of information for email replies. This opened my eyes to the huge diversity and importance of pollinators. One group of bees which I found particularly interesting were Leaf-cutter bees, which is why I decided to write a blog about them.

As well as the social living bumblebees and honeybees, there are over 225 species of Solitary bees pollinating the UK. They are called solitary bees as they have no social caste and basically fend for themselves and their offspring. Leaf-cutter bees belong to the Megachilidae family, and are a fantastic pollinating group for a variety of fruit, veg and other plants including wildflowers.

Some species, like the Silvery leaf-cutter bee (Megachile leachella) and the Coast leaf-cutter bee (Megachile maritima) can be found nesting in groups called aggregations, although each female tends to their own nest cells. However, most species choose to nest in existing cavities on their own. Leaf-cutters have been found to nest in a variety of places such as dead wood, hollow plant stems, cavities in walls and occasionally in the soil. Commonly found in gardens, these bees are widespread across the UK, though they have a smaller presence in the north.

One of the most common species of Leaf-cutter bee is the Patchwork leaf-cutter (Megachile centuncularis). Patchwork leafcutters look similar to honeybees, though the females have a patch of hair beneath their abdomen called a pollen brush. The pollen brush is used for storing pollen, as opposed to most other bees which store pollen in pollen baskets on their hind legs. Intriguingly, some Leaf-cutter species including Patchwork leaf-cutters lift their abdomen up into the air while feeding; see this video to watch this distinctive foraging behaviour. However, they are probably best known for their trick of cutting neat, semi-circular pieces out of rose and wisteria leaves to take to their nests. These bees will grasp the leaf cutting and carry it underneath their body to their nest. The Patchwork leaf-cutter will glue the overlapping pieces of leaf together with saliva to use as lining, in order to build individual cells for their eggs which are sealed off by more pieces of leaf. Within each cell, the egg is provisioned with pollen to provide the hatched larvae with essentials to grow. This pollen can come from a variety of flowers including legumes like runner beans, as well as berry flowers like brambles. The larvae will then pupate into adults in autumn and hibernate inside their cells over winter.

Make a home for the bees

Like many solitary bees, Leaf-cutters can be limited by the amount of available nesting habitats. The good news is that this is something we can all easily do something about – by creating a bee hotel. Leaf-cutters and other solitary bees are great for pollinating your fruit and veg, so why not help them out and entice those that like to nest in cavities into your garden? Bee hotels are great to watch, provide lots of entertainment and are available to buy in most garden centres.  You can also make one yourself which is cheap and easy. For 5-star accommodation all you need to do is find an untreated block of wood and drill holes of varying diameters into it (2-10mm), but not all the way through the wood. Try and make the holes as smooth and splinter-free as possible, as splinters can damage their wings. It is also important that rain does not get into it so the gaps should be created at a slight incline. The hotel should then be propped up or mounted onto a sunny, south facing wall and at least a metre off the ground. Another option is to find sections of old, hollow bamboo canes (around 20-30cm long). Tie the bamboo sections together, or place them into a plastic drinks bottle with both ends cut, and hang them horizontally in a sunny and sheltered position.

Many bee hotel designs and ideas can be found on the internet to help. It is best to replace the holes in your hotel every two years, as this prevents the build-up of fungus and parasites. Patchwork leaf-cutter can be seen between mid-June to early September, so if you can set up a home for the bees soon, you may find it is used this year. If not, it will be ready for next year’s bee season in spring!