Solitary bees

ArneStander
Published on June 12th 2020
20
A close up of a flower
Candide recently launched the #PollinationSA movement which encourages all South Africans to plant bee-friendly plants to create an environment where all bees can thrive.
Often, when we think of bees our minds can easily jump to the familiar honeybee. Probably because honeybees are the most familiar bees associated with the sweet honey which we all enjoy. But, did you know, South Africa has more than 1000 solitary bee species?
In this article, we'll be taking a closer look at solitary bees to appreciate their incredible diversity and ecology.
A yellow flower
Carpenter bee (Xylocopa sp.). Photo by @petunia_summer2.
Bees fall within the order Hymenoptera, along with ants and wasps, and are very diverse with an estimated 20 000 to 25 000 species globally. South Africa has more than 1000 different bee species, most of which are solitary species. Solitary bees are very important in keeping healthy ecosystems and play a vital role in plant pollination.
What is a solitary bee?
Unlike honeybees, solitary bees do not live in hives or large colonies. 'Solitary' literally suggests to live alone. Even though they live alone, solitary bees often nest close to one another.

General ecology of solitary bees

We are familiar with honeybees nesting in hives, whether it is the wood-fashioned Langstroth hive, or inside a dead tree. Unlike honeybees, it is not always veyr clear where solitary bees nest. There are indeed many options for solitary bees to nest. They can inhabit pre-existing cavities such as wood tunnels or hollow reeds, which were abandoned by other insects.
Probably some easy-recognizable solitary bee species are the carpenter bees. The name says it all - these bees bore tunnels in wood to lay their eggs. Carder bees construct external nests by using plant material. Dauber bees build their nests with mud or resin. Leaf-cutter bees gather small fragments of leaves to build their nests. Mining bees make tunnels in the ground. Not all solitary bee species build their own nests, however. The cuckoo bee will wait for a female to leave her nest so that she can lay her eggs in the nest.
Take a look at @dawnmacd's post below to see the cuckoo bee.
Although some solitary bee species nest in colonies, each female bee constructs her own nest. These nests also consist of several chambers which are partitioned off from each other. Females fill each chamber with a mixture of nectar and pollen, and an egg is laid in each chamber. As soon as eggs hatch, the young bee larvae feed on the nectar and pollen supply. The larvae will pupate before the adult bees emerge. Thereafter, mating will take place, usually in spring, and females will nest. The whole cycle then continues.
Visiting flowers, solitary bees have adapted brushes of hairs, either on their legs or abdomens, in order to collect and transport pollen to their nests. They are more effective pollinators than honeybees, as honeybees have sacs on their hind legs corbiculae (corbiculae) to carry pollen.
A close up of a flower
Carpenter bee (Xylocopa sp.) pollinating a Polygala flower. Photo by @frances.

Threats to solitary bees

Plant diversity is associated with pollinator diversity. Therefore, it is important to conserve pollinators as our food security and survival depends on it. Threats to bees include destruction of nests, including the removal of trees. Insecticides which are sprayed on flowers have detrimental effects on various bee species and their larvae, as the pollen is contaminated. Monocultural agriculture leads to habitat loss and scarcity of food for the bees.
A insect on the ground
Photo by @dumbndrummer.

Gardening for solitary bees

As gardeners, you can help to promote bee diversity!
- Add an insect hotel to your garden. Insect hotels can accommodate various species of solitary bees, of different sizes.
- Plant a diversity of plants, especially plants which are native to the area.
- Some parts of the garden should be left to grow wild. Leaving some areas more natural could create potential nesting sites for the bees. Something as simple as a patch of soil which can be used by ground-nesting bees.
- It is important to consider that many bee species only pollinate a specific plant species (known as specialist species). Therefore, it is better to have a diversity of plants which are local to the area. Then, your garden should be a big attraction for solitary bees to nest, forage, pollinate and thrive.
A close up of a flower
Photo by @frances.

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