Solitary bees make up the largest percent of the bee population, with 90% of bees being in the solitary category.
There are about 250 species of Solitary bee in Great Britain and 20,000 – 30,000 different species worldwide, including mason bees, leafcutters, mining bees, white faced bees, carder bees, digger bees and many more.
As the name suggests, Solitary bees are lone bees, which means they do not belong to a colony.
Only the female Solitary bee has a sting which is very feeble compared to other bees and will only ever sting you if you handle them roughly or pose a threat to them. Being loners, Solitary bees fly around by themselves and do not attack in swarms or groups like some other types of bees.
Generally, they are absolutely harmless. Solitary bees do not even bother to protect their own nests. Solitary bees create nests in hollow reeds or twigs, holes in wood, or, most commonly, in tunnels in the ground.
The female Solitary bee typically creates a compartment (a ‘cell’) with an egg and some provisions for the resulting larva, then seals it off. A nest may consist of numerous cells. When the nest is in wood, usually the last (those closer to the entrance) contain eggs that will become males.
The adult Solitary bee does not provide care for the brood once the egg is laid and usually dies after making one or more nests. The males typically emerge first and are ready for mating when the females emerge. Providing nest boxes for solitary bees is increasingly popular for gardeners. Solitary bees are either stingless or very unlikely to sting (only in self defense, if ever).
While solitary females each make individual nests, some species are gregarious, preferring to make nests near others of the same species, giving the appearance to the casual observer that they are social. Large groups of solitary bee nests are called aggregations, to distinguish them from colonies.
In some species, multiple females share a common nest, but each makes and provisions her own cells independently. This type of group is called ‘communal’ and is not uncommon. The primary advantage appears to be that a nest entrance is easier to defend from predators and parasites when there are multiple females using that same entrance on a regular basis.
Each cell will be stocked up with ample pollen and nectar to feed her offspring when they are born. She will lay one egg in each of the cells, seal it up and then fly away.
Solitary bees are very interesting to watch, you can see them regularly in your garden busying about, pollinating flowers and looking very efficient.
Solitary bees are important pollinators and pollen is gathered for provisioning the nest with food for their brood. Often it is mixed with nectar to form a paste-like consistency. Some solitary bees have very advanced types of pollen carrying structures on their bodies. A very few species of solitary bees are being increasingly cultured for commercial pollination.
Solitary bees are often oligoleges (bees that exhibit a narrow, specialized preference for pollen sources), in that they only gather pollen from one or a few species/genera of plants (unlike honey bees and bumblebees which are generalists). Oligolectic bees will visit multiple plants for nectar, but there are no bees which visit only one plant for nectar while also gathering pollen from many different sources.