Last week I found my polytunnel full of about 300 bees and had no idea why they were there. It was a mystery but now I do have a little more information.
I posted questions about the bees on Twitter and a Downsizer, a forum I am on. Several bee keepers came back to me and 2 thought that the bees may well have been attracted to the warmth which makes sense as we were having lovely sunny weather at the time with daytime temperatures in the tunnel in the mid twenties. They also thought they might be coming in to feed on the honeydew produced by aphids - but there are no aphids in there. A third thought was they were coming to drink the condensation on the plastic but again this did not seem likely as none were drinking, just bashing into the plastic. In fact the only thing I saw a few of them do (other than fly into the plastic) was to feed on the French Marigolds I have on there.
I then received some ideas about the species and I now believe the bees to be Ivy Bees. This species was only identified as a separate species - Colletes hederae in 1993 and has been in the UK since 2001 (longer in France). It is a mining bee that lives in the soil as a solitary bee but there may often be many hundreds or thousands of them in the same place. They are on the wing between September and mid November when their main food source IVY is in flower, hence their name.
|Male Ivy Bee By Charlesjsharp (Own work, from Sharp Photography, sharpphotography) [CC BY-SA 4.0], via Wikimedia Commons|