All about solitary bees

Red mason bee investigating a bee house kit from Grow Wild

When most people think about bees, they think about sociable honeybees or large furry bumblebees.

However, in the UK alone there are 267 species of bees and over 90% are not social and do not live in colonies. These are called solitary bees.

What’s so special about solitary bees? 
  • Solitary bees vary considerably in size, appearance and where they choose to nest. Roughly 70% are called mining bees and nest in underground burrows. Bees that nest in houses are called cavity nesting bees.
  • Do not live in colonies, produce honey or have a queen. 
  • Do not produce wax to construct the cells inside the nest instead different species use different materials to construct their cells and nests. 
  • Drink nectar directly from the flower and spend most of their time collecting pollen which is mixed with a small amount of nectar as food for their young.
  • Are fantastic pollinators: a single red mason bee is equivalent to 120 worker honeybees in the pollination it provides. 
  • Do not have pollen baskets for carrying pollen, meaning that each time they visit a flower they lose far more pollen than social bees, which makes them much better pollinators.
  • Provide each larvae with everything it needs but they do not tend to the young as they grow and never get to see their offspring emerge. 
  • Are non-aggressive and do not swarm.
  • Safe around children and pets.
Their place in the ecosystem

European wool carder bee feeding from a purple flowerEuopean wool carder bee

Solitary bees are easily overlooked but they are known to pollinate plants more efficiently than honeybees. 

They provide an essential pollination service, pollinating our crops and ensuring that plant communities are healthy and productive. Without them mammals and birds would not have the seeds, berries or plants on which they depend: in fact, approximately one in three mouthfuls of food and drink require pollination.

Wild flowers provide essential resources of pollen and nectar for these busy workers – and ample nesting opportunities in their dry, hollow stems. Some such as the harebell carpenter bee are so dependent on a particular wild flower plant (in this case bell flowers) they cannot survive without it.

Providing shelter for solitary bees

Each female solitary bee constructs and provisions her own nest. 

Cavity nesting bees require dry hollow tubes to lay their young. Try making your own bee house by following our step by step guide with Hannah Grows:

How and when to identify solitary bees

Bees have four wings - whereas flies have two - and are generally hairier than wasps.

Solitary bees vary massively but you can identify which ones are nesting by the materials they use to close the tubes. They usually live for a year but you’ll probably only see them during their active adult stage, over a few weeks in the spring or summer. 

Different species do appear at different times: the red mason bee is the first to emerge, hence its importance in pollinating fruit trees, whereas leafcutter bees can be active as late as September. 

What happens in the bee house

Each female bee lays 20 to 30 eggs during her life.

When a bee finds a nest she will collect materials to create the cell for her first egg: a ball of pollen stuck together with nectar for each larvae to eat until it develops into an adult bee.  

She places the ball inside the cell and lays an egg on top, leaving space for the larvae to grow into an adult bee. She builds a partition wall and repeats the process until the whole tube is filled, leaving a space at the entrance of the tube empty before closing it off and moving on to another tube.

Females choose whether to lay male or female eggs: since males emerge a couple of weeks before the females she lays all the females at the back and males at the front. 

Solitary bees spend their early months hidden in the nest growing. They then spend the winter as a cocoon (or pupa) before emerging the following spring or early summer as adults. Once the adult bees have mated, the female looks for a suitable nest and the cycle repeats itself. 

What to look out for 

bee buzzing around a bee house with tubes where they're slightly blockedSolitary bee in a house with slightly blocked tubes

You might notice bees buzzing around your house and on wet days during the flying season check inside the holes and might see them sheltering from the rain.

The only certain sign of nesting is seeing the ends of the tubes capped with either mud, leaves or fine hairs. The type of capping indicates the type of bee and it’s possible you might have more than more one type at the same time.

The three bees that you are likely to find in your bee house are:

Red mason bee

Red mason bee, Osmia bicornis (Osmia rufa) – red/gingery hair, females have small horns on their heads = use mud to cap tubes (March–July)

Leaf cutter bee feeding from flower.

Leaf cutter bee, Megachile willughbiella – broad head, large mandibles for cutting leaves and an upturned abdomen = use leaves (May–September)

Sleeping wool carder bee.

Wool carder bee,  Anthidium manicatum – distinctive yellow and black markings on the flattened abdomen  = use fine plant hairs (June–August)

Keep a record of:

  • Number/date of holes filled
  • Material used – eg species 
  • Date the cap is opened
  • Photos of the bees and capped holes

Want to find out more ways to help our pollnator pals? Read about why weeds may be bees' best friends.