…blog by Rachel Richards, Buglife B-Lines Officer, written for Solitary Bee Week 2023
In the UK we are blessed with an abundance of bee species, not just the much-loved domesticated Honeybee (Apis mellifera) and a few bumblebees, but 24 bumblebee species and over 250 species of what we refer to as solitary bees. When I tell people about these bees they often respond with something like “poor things, they must get lonely”, so let me explain a little.
Where I live in the northeast of England I have several favourite walking routes, areas which, like many, I became extremely familiar with over lock-down. Despite 16 years here and walking most days, during lock-down I discovered new bee hot spots on my doorstep including a very busy bee bank, home to many species of solitary bees.
Solitary bees nest in a variety of places depending on the species, but broadly speaking we divide them into aerial nesters, which use holes in dead wood, between bricks, etc. (the ones which use bee hotels), and ground nesters. Within the ground nesters different species prefer different soils. No doubt you can guess the preferences of the Sand Pit Mining Bee (Andrena barbilabris), in my area I find it on sandy riverbanks.
My local bee bank is a small path-side cutting in clay, the type of cutting made by livestock and people regularly using a certain route. It’s south-east facing so gets lots of sun, and over the years I have noticed a fascinating succession of bee species nesting here from spring through to late summer. On a nice sunny day, this is a busy place. If bees get lonely, I don’t think these do, but living here definitely has other challenges!
The first bee species to appear here in numbers from mid-April is the Buffish Mining Bee (Andrena nigroaenea), this is a large solitary bee, about the same size as a Honeybee, and like many solitary bees the males emerge first and often in good numbers. Twenty to 100 bees may be seen looping around the bank ready to pounce on the first female they can find, sometimes pulling her out of the hole she is emerging from, falling on her in numbers and rolling in a ball together down the bank. It can’t be an easy life being a female mining bee! As more females emerge and are mated, males die off and the bank becomes busy with females digging tunnels, collecting pollen from Gorse, Willow, Hawthorn, etc., and provisioning each egg with pollen and nectar before sealing the cell and laying another. Once a tunnel is filled with provisioned egg cells the tunnel is plugged with soil and another is dug. The bee bank isn’t without dangers however…
Circling around an active bee bank you will almost always find parasitic species. These are not evil, as we so often like to think in our anthropogenic way, but in this case these species have developed the intelligence to exploit another species rather than wasting energy working to feed their own young. We all love Cuckoos, don’t we? I know I do. Within the solitary bees (and bumblebees) there are a number of cuckoos, the Nomad Bees (Nomada), Sharp-tailed Bees (Coelioxys) and Blood Bees (Sphecodes) – they are red; no other link to blood. When I first saw a Nomad Bee, I was convinced they must be wasps; they look like small wasps until you get your eye in. Nomads can be yellow and black, red and black or the trickiest to identify, red, yellow and black and each species has its preferred host or hosts.
Our busy female Buffish Mining Bees, minding their own business provisioning their nest cells need to be on constant look out for nomads, in this case a large(ish) black and yellow Gooden’s Nomad Bee (Nomada goodeniana). Following chemical cues, the nomads hover around any open nest tunnel they can find, waiting for the female to pop of for more pollen before sneaking in to lay its own egg. If it is successful, when the nomad larvae hatch, they will predate the bee egg or larvae then move on to its food store, emerging the next spring/summer instead of the host.
Another fascinating parasite is the rather popular fluffy bee mimic, the Bee-Fly. In northern England we only have the Dark Edged Bee fly (Bombilius Major). They may look harmless, in fact if you catch one for a closer look, handle with care, they are rather delicate, but they are not harmless to their hosts. They hover around bee banks with their proboscis extended and are often seen sipping nectar from flowers but at just the right moment they will turn and fire their eggs in to the open, unsealed egg chamber of a solitary bee and fly on as though nothing happened.
In early May when nesting Buffish Mining Bees have reached good number on the clay bank face Ashy Mining Bees (Andrena cineraria) start to appear, later followed by Lathbury’s Nomad (Nomada lathburiana). Again, large number of male Ashy Mining Bees emerge first and may increase in number over a week or two until the first females are spotted. These furry black and white bees, quite panda-like in their colours and nice and easy to identify, seem to get on well nesting with the Buffish Mining Bee as they prefer the short grassy area above the bank face. It’s a wonder all these bees manage to avoid digging out the sealed nests of other bees. After the Ashy Mining Bee, Wilkes Mining Bee (Andrena wilkella) is found from late May followed by Base-banded Furrow Bees (Lasioglossum sp.) and their parasites, Blood Bees.
Though most solitary bees do not live in a shared nest with a queen and many workers, like Honeybees and bumblebees do, most do not nest alone. Many species nest in aggregations (like bee housing estates) as the two mining bees mentioned do and some share a nest entrance and make their own side tunnels, while a few, like the Common Furrow Bee (Lasioglossum calceatum), often produce a small number of slightly smaller infertile worker bees to help provision nest cells.
Though we have only discussed a few of the solitary bee species using this bank, over 14 species have so far been recorded nesting here. These nesting areas are vital features in the landscape and fascinating to observe. Perhaps you have something similar on a local walk, in your garden or on your farm? Next time you are out for a walk keep an eye on those sunny banks and see what you can spot.
Join us & celebrate the wonderful world of solitary bees!
90% of bee species are solitary bees and along with other pollinating animals their hard work is responsible for at least one in every three mouthfuls we eat. However, like many species, they are under threat and need our help.
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