There are around 20,000 species of bees in the world, the vast majority of which are solitary bees.
In the UK we have 267 species of bees, of which around 240 are solitary bees.
As their name suggests, solitary bees don't live in colonies like honey bees and bumblebees but lead far more solitary lives.
They never swarm, and do not produce honey or have a queen.
Solitary bees are unaggressive. The males generally have no sting and the female will only sting under extreme circumstances - such as being trodden on.
Different species appear at different times: the red mason bee is the first to emerge, whereas leafcutter bees can be active as late as September.
Solitary bees over-winter as pupa. They emerge as an adult insect in Spring or Summer and may then live for a few weeks.
The majoirity of British solitary bees nest in the ground, excavating their own nests. The nest chamber is dug exclusively by the female. Several eggs are laid in each pollen-lined chamber but each one is seperated from the other by a partition wall. The chamber is then sealed up.
Favoured areas may attract a small concentration of nests, but their owners do not interact with each other.
Some species nest above ground, typically using old beetle holes; these are the species most likely to use artifical nests. Look out in particular for the red mason bee, the leaf cutter bee and the wool carder bee.
Red mason bees seal their nest chambers with mud, leaf cutter bees use leaves and wool carder bees favour fine plant hairs. These are important clues to indicate which species of bee is in residence.
A single female will lay between 20 and 30 eggs during her lifetime.
Solitary bees are highly important pollinators. Most collect pollen on their legs on specialised hairs called the scopa.
It has been estimated that a single red mason bee is equivalent to 120 worker honeybees in the pollination it provides.
Some species, including the leaft cutter and mason bee, collect pollen on specialised hairs on the underside of their abdomen.
Not all bees collect pollen: around a quarter of British solitary bees are brood parasites or cuckoo bees. They rely on the pollen of their hosts to provide for their offspring.
Like a cuckoo, these bees seek out suitable nests in which to lay their eggs. The host's larvae are either killed by the cuckoo bee or by its own larvae. The latter then eats the pollen in the nest chamber.
Cuckoo bees are rare and most look like wasps than bees, their bright warning colours protecting them from predators.
Most of our solitary bees are polylectic which means they collect pollen from a wide variety of plant species.
However, several solitary bees specialise in collecting pollen from one genus or species of flowers or plants; this is known as oligolecty.
Plants from the daisy and pea families are among the favourites of the bees that practice oligolecty.