Solitary bees can be overlooked in favour of honey-producing bees, but their importance as pollinators simply cannot be underestimated.
Honeybees and bumblebees we all know, even though many of us have trouble naming them. But solitary honeybees? Most of us don’t know much about them, but out of the 270 types of bees found in Britain there are nearly 250 solitary species. It may seem like a lot but there are 20,000 bees species worldwide. In these isles you will find 24 different species of bumblebees, as well as a single honeybee species.
Even experts have difficulty identifying a few of the solitary honey bees. For the most part, a microscope will be needed to identify the majority of solitary bees. Submarginal cells of the forewing and the shape of their tongue are important for identification. It’s a highly complicated business and explains why so few have anything other than a scientific name.
A large number of solitary honey bees form a group
Solitary bees are aptly named, as they don’t live in colonies like honeybees or most bumblebees. More than half of solitary bees nest underground, excavating their own chamber. The solitary bees, however, are an incredibly diverse and varied group, so many of them follow a different set rules. Some build so-called ‘aerial nests’, typically taking over old beetle holes in vegetation. A metallic-blue bee is another species that lives alone. Ceratina cyaneaThis is a bird that excavates a nest for itself, which it usually does in bramble stems. It excavates the stem pith to make space for its eggs. There is also a trio of snail-shell-nesting bees, using empty shells for their nests – a remarkably sensible arrangement.
Although there are different families of solitary honeybees, all of them feed on nectar and pollen, which makes them an important pollinator in the countryside. This is to the benefit of the ecosystems as well as the agricultural industry. While honeybees often get the credit for pollinating plant species, studies have shown solitary bees to be two or three time more effective pollinators. There’s a simple reason for this. The pollen that a bee collects after visiting a flower can stick to its body. Honeybees are the ones who usually carry this pollen back to their hive, but solitary honeybees visit more flowers and spread it. They also require less pollen as a food source as they don’t live in hives.
They are often overlooked despite their vital pollination role
Solitary bees are often overlooked and their value is not fully appreciated despite their importance as pollinators. Despite the fact that there are few studies on these bees, we know their numbers have dropped dramatically over the past decades. Climate change and increased pesticide usage are two factors, but the biggest problem is habitat change. Converting wild habitats into agricultural landscapes has a huge impact on insects, which depend on floral diversity to survive. Wild bee populations cannot survive in large monocultures.
My neighbour, who is concerned about the soil quality on his 1,000-acre property, has turned to regenerative agricultural practices. He joined me when I undertook a GWCT Big Farmland Bird Count on his farm, explaining to me that what he called “cides” – that’s pesticides and herbicides – are cheap, so farmers are encouraged to use them even if they haven’t got a problem. “The argument goes that you might just as well use them, as a sort of insurance, as if you don’t you might find you have an infestation of aphids or whatever,” he said. “If pesticides were three or four times the price, then they would be used much more selectively.”
Too liberal use of pesticides and herbicides
He then told me that for various reasons, he no longer grows sugar beet. He explained that he has decided to stop growing sugar beet because of a number of reasons. One was the damage done to his light soil by harvesting it. Another major concern is the use on sugar beet seeds of neonicotinoid to control the aphids. Aphids do not pose a major problem for sugar beet seed, but they are responsible for spreading viruses like beet Yellows virus, beet Chlorosis virus, and beet Mild Yellowing virus. In 2023 the Government has once again authorised “the limited and controlled use” of the product Cruiser SB, which contains the neonicotinoid thiamethoxam, for the treatment of sugar beet seed. The neonicotinoids, or “neonics”, are dangerous to bees. Wild honey bees in particular are at risk.
To protect solitary bees it’s vital to make as many people as possible aware of their existence, not to mention their importance. The mining bees are the easiest to identify of all the solitary bees. There are 65 species in the genus AndrenaThe largest bees in Britain are of this genus. The size of these bees is highly variable, the smallest being only 5mm and the largest over three times as long. They are named after the fact they nest in the ground. These bees have a short pointed tongue and are distinguished by the grooves that run down the inner surface of their eyes. All bees collect pollen at the back of their legs.
Easily identify solitary bees
The fact that many of these bees are easy to identify and see is reflected in their English names. The tawny miner bee is a classic example. It’s a spring-flying, common bee you may find nesting on your lawn. Around the mouth of the burrow, it creates little mounds that look like miniature volcanoes. The bees are brightly colored ginger. Females are larger than males and have white hairs on the face.
The wool carder bee also known as the leaf-cutting, or mason bee is a distinctive species. It’s an attractive, robust, bicoloured insect that collects hairs from plants to build its nest, behaviour that was first noted by the naturalist Gilbert White in his garden at Selborne in the mid-18th century. The males are larger than the females, and they are very territorial. If you look closely, you can see them protecting a patch of flower for their mate. They don’t have stings but they will wrestle any insect that invades their territory, even crushing intruders to death. This species, which is most common in southern England from May to August, can be seen on the wings.
Old buildings are often inhabited by masonry bees
Red mason bees are among the most common solitary bees. They nest in the crumbling cement of old buildings. But they will also use plant stems with hollows, or holes in cliffs. The species can be found on the wing in late March and is most often seen in urban environments. It prefers gardens and parks. They are often found feeding on trees and shrubs that bloom in spring, such as apples and pear trees. The bee is particularly important in pollinating apple orchards. It is also attracted by oilseed rape.
Red mason is an easy to recognize species. The box-shaped top of the head has distinctive curved horns that are not seen in any other British species. Red masons possess brown-haired, thoraxes with orange-haired abdominals. In a structure called a pollenbrush, the females collect pollen from these orange hairs. Depending on the colour of the pollen, it can make the bee’s underside look unexpectedly bright.
You can identify bees by watching how they move.
Birdwatchers describe identifying birds based on their distinctive jizz. You can learn to identify bees with a bit of practice. Hairy-footed bees are among the first solitary insects to emerge each spring. They can be easily mistaken for a small bumblebee. But while bumblebees have a bumbling flight, hairy-foots have a distinctive quick, darting flight action – a good way to pick them out. This species, like many solitary bees exhibits strong dimorphism in the way that males and females look. The males are gingery brown while the females have all black except for orange hairs at their hind legs. Although they are called solitary, they nest in noisy and large groups.
The best way to help solitary honey bees is by planting nectar mixes in our gardens and farms. Vetch, clovers, lucerne, ox-eye daisies, knapweed and bird’s-foot trefoil will all be appreciated by our solitary bees, along with the more obvious bumblebees and butterflies. These mixes not only add vibrant colour to the countryside but also provide a lifeline for a group insects that we depend on, unknowingly.
How to make bee hotels
They are available at an affordable price from garden centres and manufacturers of bird boxes. But they can also be made yourself. Start with a wooden box that doesn’t have a front. If the box is small there’s no need to compartmentalise it, but a larger box will benefit from being divided into sections. Pack each one with hollow plants or reeds – the greater variety of size, the better. Each plant should be cut down to the depth of your box. You can include wooden blocks drilled in different sizes with deep holes, as well as hollow stems. It is important to choose the right location for your box. Solitary bees prefer warmth and sunlight, so make sure it faces south and is near flowers and shrubs that are bee friendly. It can be anything up to six feet from the ground and should be fixed so it doesn’t move around. The end of the hole will have mud or leaves plugged in. The bee-grubs will spend the winter in the box before emerging the following spring.
Learn more about how you can help wildlife.
You can find more features like this on the The Field‘s conservation content. You can read about rewilding here and learn how to create a garden that will help insects here.