Ivy bees are in a league of their own

Bees are surrounded by a buzz of concern and publicity. Are they dying out? Are pollinators in crisis? Can gardeners save them? The subjects are complex and soundbites do not do them justice. In recent weeks I have been watching particular bees as they go about their seasonal business. I have learnt facts which have not featured in the discussion.

I have been observing them in the front quadrangle of my Oxford college. It has a mown circular lawn, the first greenery that tens of thousands of visitors see when they enter. Discreet signs at ground level tell them “Please keep off the grass”. Only for one brief interlude did exquisite Oxford wits change the message. Overnight they split the metal signs, removing their left-hand sides. The letters “pl” fell off “please”, “gr” fell off “grass”, and “keep” disappeared entirely. The remaining letters fascinated the first tourists of the morning. I remember watching as Japanese visitors knelt down to film them. Two Germans declared them toll, splendid.

Normal messaging has resumed but at grass level bees are ignoring it. Dozens of them have been hovering by the edge of the lawn beside small heaps of earth which they have excavated. They have not only trespassed on the lawn. They have trespassed underneath it.

What sort of bees are they? There are about 270 species of bee in Britain, 24 of which are species of bumblebee. The bees by our grass are not bumbles. With the help of a handbook, I identified them at first as miner bees, but a scientist then brought clarity. My colleague Jonathan Green, a member of Oxford’s department of biology, recognised them as ivy bees, examples of Colletes hederae. Georgia Drew, formerly in the department, had studied them in her doctoral thesis. Brilliantly, they have explained to me what is going on. Ivy bees are increasing in British parks and gardens but the buzz in the press has yet to pick them up.

Even when ivy bees nest under mown grass, they only emerge at the end of summer. So far from declining or being at risk, they have colonised south England and Wales and are rapidly moving north within flying range of flowering ivy. In September and early October, grey-green heads of flower proliferate on Hedera helix, the common ivy. It abounds in Britain, an ivy that grows uninvited on the walls and fences of many gardens.

Ivy bees’ emergence coincides with the weeks in which they can draw nectar, rich in sugar, from this ivy’s autumn flowers. It gives them energy, varyingly expressed. As an onlooking classicist I remember how Greeks and Romans drew parallels between bee communities and human society. They were never more finely expressed than in Virgil’s great poem The Georgics: as I watched our bees I began by seeing a parallel between some of their habits and life a generation ago in the college they have chosen to colonise.   

Under the lawn, each female ivy bee digs a corridor. Unlike a honeybee or a bumblebee, she never shares it with others. Ivy pollen gives her the strength to dig it and she returns to it with a coating of the pollen’s yellow dust on her legs. Off her self-made corridor, she digs little rooms, or oval-shaped chambers. In each one she deposits one of her eggs, with sufficient pollen for the egg to hatch and develop into an adult.

I saw parallels between the bees’ habits and life a generation ago in the college they have chosen to colonise

In the following September, when the ivy is about to flower, young ivy males emerge from the underground rooms into which their mothers had deposited them a year earlier. They hang around the entrance to the females’ corridors, waiting for them to come out.

In 1979, after 600 years, New College finally admitted women as undergraduates. Like male undergraduates, each received a
room of her own. They too lived on corridors, not underground but up steep stone staircases, round whose entrances males sometimes hovered hopefully, looking to ask them out on dates.

In the bees’ own ivy league, the males do not stop at dating. Aristotle and Virgil shared a widespread ancient view that bees never have sex. In the past few weeks we have watched our college lawn and refuted them. When a female bee comes out, the males fly at her, forming what scientists call “mating balls”. Every three years, in June, we have balls on our college lawn, but they are totally different occasions. They are Commemoration balls, which begin on a red carpet laid above the grass. The bees are still dormant in their corridors below. 

In the scrum of a mating ball the bigger male bees collide and jostle. The smallest male bee appears to have the best chance. Afterwards, the female goes off to find ivy flowers and returns with pollen for her future larvae. It is likely, but not certain, that she will never mate again. The male bees manage several repeats. Eventually, we have found that they crawl post-coitally to the stone threshold of a nearby room in which our chapel choirboys rehearse. Do they want to expire to the sound of music?  

Under and beside our lawn this yearly drama qualifies one-sided views that mowing is an enemy of biodiversity. Ivy bees are one of the types of biodiversity that thrive in mown grass: a good guess is that the soil beneath a lawn is warmer when they mature and are preparing to emerge.

Ivy bees also counter fears about an autumn shortage of pollinators. They emerge too late to pollinate fruit trees, but they pollinate other garden flowers, at least until the ivy flowers are open. They have been found to carry other pollens on their legs, including the pollen of Michaelmas daisies and clematis.

Bees need friends in farmland and woods, but do you want a ball of bees buzzing beside the main path of your garden? We allow weddings in the nearby college chapel, but after the first sighting of ivy bees, an autumn bride, preparing to enter the aisle, walked past the lawn and was stung near her neck. Onlookers blamed the ivy bees, but they reacted too hastily.

In 2019, scientists from Sussex university studied a colony of 2,500 ivy bees near Falmer. One of the researchers spent 10 hours among them and was stung only once. Male ivy bees turn out to have no stings and half of the females sting too feebly to penetrate human skin. The only one who did so caused no more pain than a nettle. The bee that stung our bride was not an ivy bee, wishing to warn her from her own experience. Ivy bees are multiplying, and we should appreciate them, not fear them.

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