Well, it’s already mid-September, which means that the bulk of this year’s records have come in and we are able to see some of the emerging patterns (though more detailed number-crunching will take place over the winter). There is very strong seasonality in bumblebees; August sees a super-abundance of male Buff-tailed Bumblebees, Bombus terrestris which are quite variable in their band colour (which ranges from quite bright yellow to buff-brown) and tail colour (mid-buff to almost pure white). This has led to many being misidentified as the White-tailed Bumblebee, B. lucorum and sometimes Garden Bumblebee, B. hortorum. In most submitted photographs, I am able to distinguish a male terrestris from a worker using body shape and the extent to which the pale collar behind the head extends down the side of the thorax. Once sexed, it is a much easier species to confirm, because male White-tailed Bumblebees look rather different. Garden Bumblebees have the yellow band across the body in a different position – you may have seen our recent tweet showing photos of this.
It probably helps that I’ve done lots of field recording of bumblebees along arable margins for the Centre for Ecology & Hydrology this summer, so a lot of practice separating bumblebees with white tails and yellow bands!
Since the end of August, the Common Carder Bee has become the most frequent species spotted by our app users, and records include both males and workers. This species is known for foraging well into autumn, and gardens with an abundance of late-flowering plants suit it nicely. Males love dahlias, but workers prefer Penstemon blooms.
It is nice to report that a few records of scarcer species in gardens have appeared, most notably two records for the Ruderal Bumblebee, B. ruderatus. This can be a very difficult species to distinguish from the Garden Bumblebee, B. hortorum, but it has shorter, neater body hairs and workers have browner, narrow bands across the body. By sheer coincidence, one of those records (from Essex) was only one mile from a farm I had surveyed during the summer and seen lots of ruderatus. These sorts of observations highlight the way in which both urban and rural habitats contribute to the survival of an individual bumblebee species.
Bumblebees will continue to forage for a few more weeks, so keep sending your photos in, and remember that records without photos cannot be used in our number-crunching, so please try and take a picture; I can often identify the species from really fuzzy images. Thank you for all your time. I think Blooms for Bees is a shining example of citizen science working well – plus it is a lot of fun.