As the common heather (Calluna vulgaris) reaches full bloom and creates patterns of pink across the hillsides at RSPB Dove Stone it is time to get out and have a look for what might be the reserve’s most abundant solitary bee; Colletes succinctus, the Heather Colletes.
There are just nine species of Colletes in the UK. These include the newly arrived Colletes hederae (Ivy colletes), Colletes halophilus (Sea-aster Colletes, one of the UK’s rarest bees) and of course our very own Colletes succinctus. All Colletes are very smart looking bees with strong bands of short hair on their abdomens, beautiful golden-orange hair and heart shaped faces.
Like all solitary bees Colletes nest individually. A lone female digs a nest burrow in a sandy earth bank within which she constructs an individual cell for each egg that she will lay. She produces a cellophane-like material from glands near her mandibles with which she ‘plasters’ the cell to create a waterproof and fungus-resistant lining. Because of this Colletes are also known as ‘plasterer bees’ and have specially shaped tongues to apply this lining to their nest cells.
Once plastered each cell is provisioned with a mix of pollen and nectar, collected almost entirely from heather, onto which a single egg is laid. A bee larvae will hatch from the egg, consume it’s provisions and after a few weeks transform into a pupa. It will remain as a pupa within the nest burrow protected from harsh conditions over the winter season and then emerge as a fully-grown new bee once the heather starts to bloom the following year.
Although they are solitary bees Colletes often nest close together in large aggregations in suitable exposed patches of bare earth, especially those that face more or less South East and are well warmed by the sun. Like all bees Colletes need warmth to fly and for their larvae to grow.
Colletes succinctus forage mainly from heather for both pollen and nectar so they can be seen on the wing during August and September when the Calluna is in full bloom. Dove Stone provides an ideal habitat for them with it’s profusion of heather and patches of sun warmed bare earth. There are often aggregations of Colletes succinctus at many suitable locations around the reserve. One especially good place to see them is on the earth bank near to the bridge at Ashway Gap (but please be careful not to tread on them). Earlier in the season you can see hundreds of male Colletes, which emerge from the nests before the females, flying low back and forth across the aggregation searching for emerging females to mate with.
The nest building females are fascinating to watch as they forage from the heather scattered around the reserve, if you look closely you should be able to see the yellowish pollen they have collected packed tightly onto the scopa (pollen collecting hairs) on their hind legs. Of course there will also be plenty of other insects enjoying the profusion of heather to keep an eye out for including bumblebees, hoverflies and ladybirds.
You may also be lucky enough to see another solitary bee, Epeolus cruciger. Epeolus cruciger is a cuckoo bee (or cleptoparasite) which sneaks into the nest burrows of Colletes succinctus and lays it’s own egg on the provisions stored there. The Epeolus larvae will consume these provisions before the Colletes larvae to it's obvious detriment.
Like all solitary bees Colletes succinctus are harmless and are very important pollinators and a vital part of our ecosystem. They are very attractive bees and fascinating to watch so please keep an eye out for them on your next visit to Dove Stone.
Even though it is getting towards the end of summer and the weather is getting cooler there are still many fascinating invertebrates active and worth seeking out, I have not yet seen Mellinus arvensis (the field digger wasp and possible star of my next blog), which is a sure sign that autumn is coming.
Enjoy your bee watching!
More info and references:
https://www.bwars.com/bee/colletidae/colletes-succinctus
https://bwars.com/sites/www.bwars.com/files/info_sheets/19_Colletes_succinctus_1col_infosheet.pdf
Handbook of the Bees of the British Isles by G. R. Else and M. Edwards. (isbns: 9780903874519)