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Solitary Bees |
Class: Insecta Order: Hymenoptera |
Most solitary bees resemble
small honeybees or, in some cases, small bumblebees, but the adults of most
species are fairly short-lived and seen for only a few weeks in spring or
early summer . . . . . . |
There are over 200 species of solitary bees found in
Britain and, like the social bees (the bumblebees
and the honeybee), they all feed on pollen and nectar and they are important
pollinators of many garden flowers and commercial crops. Solitary bees
have no 'workers' and each female builds only a small nest, which she
stocks with a large quantity of pollen - enough to provide all the food
needed by her future offspring. After laying her eggs, the female bee
seals and abandons the nest and soon dies, leaving her offspring to
develop on their own.
Many solitary bees nest in the ground
and seal the nest with soil (these are commonly known as mining bees,
e.g. species of Andrena). Others nest inside the hollow stems of
plants or inside holes and crevices in brickwork, stone walls, dead trees,
fence posts and other timber, sealing the nest with mud (mason
bees, e.g. Osmia species) or pieces of freshly gathered leaves
(leaf-cutter bees, e.g. species of Megachile). Leaf-cutter
bees sometimes cause damage in the garden by cutting large, more or less
circular holes in the leaves and petals of roses and other plants.
The Tawny Mining Bee (Andrena fulva) is one
of several species, commonly seen around gardens in early spring, which dig nest
burrows in lawns and similar places. This bee is about the same size as a
honeybee, but covered with fairly dense golden hairs. |

Nest holes in a garden lawn (left & centre) excavated by the female solitary tawny
mining bee, Andrena fulva (right) |
The female bee makes a small volcano-like mound with
the soil excavated from the nest. There may be many nests close together,
giving the impression of communal life, but each female is actually working
alone. Nesting activity lasts only a short time (perhaps 2-3 weeks),
after which the small mounds of earth around each nest entrance soon
disappear, with no permanent damage to the lawn. Take care not to
confuse solitary bee nest mounds with the mounds of earth caused by
the nesting activity of ant colonies. Solitary bee mounds have a single
large entrance hole in the middle, and by watching for a short while on
a warm sunny day, you will see the bees coming and going to collect
pollen.
If left alone, these bees will often nest in the same
area year after year, and provide an annual service by pollinating your early
flowering fruit trees and shrubs (apples, pears, currants and gooseberries)
and other garden plants - so helping to ensure good crops later in the
year.
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Another group of solitary bees
are the so called carpenter bees (Ceratina and Xylocopa
species). These bees tunnel into plant stems and wood, often causing
damage, and thus are less welcome around the home and garden. Most tend
to be fairly gregarious with several females making their individual
nest-tunnels close together. The lesser carpenter bees (Ceratina)
are fairly small (5 mm or so in length), and usually black or metallic blue
or green in colour. Most of them excavate nest-tunnels in the central pith
of plant stems such as sumac and raspberry. The large carpenter bees
(Xylocopa species) resemble large bumblebees in general appearance,
mainly black in colour, but sometimes with dense yellow hair on the thorax
(the body section where the wings attach - see below). These bees usually
attack fairly solid wood (e.g. dead unrotted trees and tree-stumps, felled
timber, fence posts, etc.). They sometimes tunnel into the timbers and
beams of houses, barns and other buildings, and may cause considerable
structural damage if left unchecked. Each bee excavates a large
nest-tunnel, often over 30 cm long, divided off into a number of separate
cells by partitions of chewed wood chips. Each cell is stocked with a mass
of nectar and pollen on which the female lays an egg. Like other solitary
bees, when nesting is finished the female bee leaves her eggs and grubs to
develop on their own, through to the next generation of adults. |
The great carpenter bee, Xylocopa virginica, is common in many
parts of North America. This bee is over 25 mm long (about the size of
a very large bumblebee), with dense yellow hairs on the thorax, a shiny
black abdomen and brownish wings. |
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The blue carpenter bee, Xylocopa violacea, is found in southern
and central Europe. It is also about 25 mm long, but glossy black all
over with sparse black hairs. The opaque wings are dark brown with a
lilac-coloured sheen. |
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MORE ON BEES & THEIR ALLIES Order Hymenoptera
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