Tuesday, 2 July 2013

Harebell Carpenter Bee (Chelostoma campanularum): The Bee who loves Bell Flowers

Harebell carpenter bees (Chelostoma campanularum) are tiny solitary bees which are mostly found in or near bell flowers, especially harebells (Campanula rotundifolia), nettle-leaved and clustered bell flower (Campanula trachelium and C. glomerata). They are quite common in gardens, parks and other urban habitats in the South of England but often overlooked and can easily be mistaken for flies.

The bees are very small (6-7 mm) and black in colour. The males have a two-pronged peg at the last abdominal segment whereas the females have pale pollen-collecting hairs underneath the abdomen. They fly from mid-June to August and you will often see them in groups of many individuals swarming around bell flowers on warm and sunny days. Males often stay in one flower for several days in bad weather and even sleep in the flowers over-night.

This patch of harebells is swarming with Harebell carpenter bees
Mating takes place in the flowers, here you see both female and male together

The female bees will only collect pollen from bell flowers and have an interesting way to collect it. They fly to the anthers, grab them with their mandibles and rub their abdomen against the anthers to transfer the pollen into the pollen-collecting hairs underneath their abdomen.

A female bee collecting pollen
This female bee is waiting for a male in a flower

Harebell carpenter bees nest in small holes such as woodworm or other beetle holes in fences and sheds. You can attract the bees to your garden if you provide some nesting opportunities (such as dry reed stems) and plant some bell flowers. They seem to be especially fond of harebell (Campanula rotundifolia) thus planting this bell flower gives you the best chance to attract the bees.

A little bee approaching a harebell flower
Harebell (Campanula rotundifolia) is an attractive garden plant

So next time you see something tiny and black flying around bell flowers have a closer look, it could be the Harebell carpenter bee.

3 comments:

  1. Great story - I was wondering what type of bees these were as they feed on clustered bellflowers in my garden, Does this suggest a benefit to growing native wildflowers in gardens?

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    1. I think it is always good to have a least some wildflowers in the garden as you will get a greater diversity of insects and other wildlife. But non-native garden plants have their uses as well, some flower really early or late in the year and provide much-needed nectar-and pollen sources when native wildflowers are not in flower yet.

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