Identification

Solitary bees are difficult to describe as there are many species that vary widely in their appearance. Some resemble small honeybees, others small bumblebees, while others could be mistaken for small wasps. Solitary bees differ from honeybees and bumblebees in not being social insects. A female solitary bee constructs and provisions her nest without the assistance of any worker bees. Despite this some solitary bees can be gregarious, with many bees making their nests in close proximity in a suitable piece of habitat.

Some solitary bees act like cuckoos, in that they are unable to make their own nests and instead enter the nest of another suitable host bee and lay their eggs there. When the cuckoo bee’s eggs hatch, the larvae make use of the nectar and pollen food store provided by the host bee.

Size

Very variable. The smallest solitary bees are 3-4mm long, the largest are about 15mm.

Distribution

Solitary bees occur throughout Britain but some are confined to particular habitats or regions.

Status

There are about 250 species of solitary bees in Britain. Some are rare and threatened by loss of habitat for nest sites or suitable flowers from which they can forage.

Habitat preference

Gardens, grassland, heaths, woodland rides, brown field sites. Many solitary bees make their nest tunnels in the ground, choosing either bare soil or areas of short turf, such as lawns. Other solitary bees nest in tunnels made in rotten wood, or they make use of vacated tunnels in dead wood made by wood-boring beetles. Artificial nest sites can be provided by drilling holes 2-8mm in diameter in fence posts or hanging up bundles of hollow plant stems, drinking straws or cardboard tubes.

Where to find them in the garden

Nest sites are likely to be in the lawn or where there is compacted bare soil. The vertical nest tunnel is topped by a conical heap of fine soil with an entry hole in the top, like a miniature volcano. Solitary bees will visit a wide range of flowers to collect nectar and pollen, which they use as a food supply for their larvae. Some solitary bee species will only collect pollen from a particular species of plant, some will collect pollen from a few closely related plants, others will take pollen from a wide range of plants.

Role in the garden

Most solitary bees are useful as pollinating insects. When they visit a flower, they pick up pollen on their hairy bodies. This pollen gets transferred to other flowers of the same species as the bee travels around, bringing about pollination. Many flowers are dependent on insects for pollination and without this service, they cannot set seeds. Solitary bees, like bumblebees, can fly in cool or drizzly weather, unlike honeybees that stay at home during inclement weather. Solitary bees can be important pollinators of fruit trees and bushes, which flower in the spring when poor weather often occurs.