The Harebell Carpenter Bee - Chelostoma campanularum

09th July 2012
This month saw the first flowering of a Campanula persicifolia or Peach-leaved Bellflower, that my wife had planted in our garden. In keeping with its name, the plant has attracted the Harebell Carpenter Bee (Chelostoma campanularum). A few years ago, I would probably not even have noticed this lovely little insect, but having been bitten with the "solitary bee bug", I now look at all potential examples, however small and "un-bee-like". And the Harebell Carpenter Bee is small. At just 5-6mm long and about 1mm wide, it could be easily overlooked. This tiny black bee is associated with the flowers of various bellflowers (Campanula species) and is common and widespread in much of England (particularly the southern half) but is absent from Wales, Scotland and Ireland.

This bee would be difficult to identify "on the wing", but has the useful habit of "resting" inside Campanula flowers overnight, or when the weather is wet or cold. A quick look around our plant in the morning, usually shows several blooms with resident Chelostoma bees, mainly males at the moment. The males wait for females inside the flowers, and mating takes place there.

So, having found a Campanula flower and then having found a tiny black bee inside, how can you tell whether it's the Harebell Carpenter Bee? I have seen other small bees on and around our plant. Firstly, both sexes are roughly the same size and both black. The male however, has a useful diagnostic feature, (if you can see it!). The tip of the abdomen is modified into a two-pronged "peg". This is just visible in the image (top left) and is a diagnostic feature for the male of this species. It is just visible with a decent hand lens (I have tried it). The structure is said to help the male bee hold on to the inside of the flowers when they are sheltering there.

The female doesn't have this, but does have a scopa of white hairs under the abdomen. The scopa is used by the female to collect pollen. The male does have hairs under the abdomen, but these are much more sparse. Both sexes also have sparse white/yellow hairs on the head, thorax and other areas of the abdomen. The males that I've seen have slightly more "facial" hairs.

Chelostoma campanularum is typically on the wing from June to August. If you happen to be passing any Campanula flowers during that time, do stop and have a close look for this little bee!

Images above: Left - close-up view of male abdomen with prongs, Centre - Campanula flower (bee inside central bloom giving idea of size/scale), Right - female just showing white-haired scopa.

Click on images for a larger version.


Photo comment By Africa Gomez: Beautifully illustrated, informative shot. I shall keep an eye for this tiny beauty in my campanulas.
Photo comment By John Lampkin: Stunning.Thanks for putting this together. I had a Chelestoma philadelphi on my Mock Orange this spring. Since Mock Orange = Philadelphus, it's a safe bet that the bee was named for the flower and will be back next Spring. I'll check for the mating behavior you describe.

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