Dear Readers, there is something about spotting a ‘new’ species of animal or plant that always makes my pulse race, especially when it’s one that I’ve been looking out for for a while. So it was on Saturday, when a birthday visit to the National Archives at Kew with my husband to see an exhibition about the Cold War had the unexpected bonus of a splendid stand of ivy flowers in the grounds. They were abuzz with all manner of hoverflies, some wasps and the usual honeybees, but then I noticed that some of those ‘honeybees’ had distinctive black and yellow-striped abdomens. There was also something about the way that the pollen was gathering in the hairs on the legs, rather than being neatly tucked away into the proper ‘basket’ that I’d expect to see on a honeybee. At last! I’d spotted an ivy bee, and it wasn’t long before I had my eye in and saw several dozen. The photos this week were taken with my phone as I hadn’t expected to ‘get lucky’, so please forgive the quality.
First things first. Ivy bees were first spotted in the UK in 2001, and since then have been steadily advancing north – their range includes most of Europe, as far south as Cyprus. They are on the wing in late autumn when the ivy flowers, and it is used as a source of pollen and nectar. Ivy bees are solitary bees – they don’t congregate in communal nests, but have build nest tunnels, although the bees may nest in the same small area, sometimes creating conglomerations of thousands of individual nests. These are the last of the British bees to emerge – I have noted before that the emergence of solitary bees seems to be in strict sequence. In my garden, the first to appear is the hairy-footed flower bee in early spring, followed by the ashy mining bees. I intend to pay closer attention next year to see who pops out when.
The ivy bee males emerge first, and hang around the nest tunnels looking for females. The first females to turn up may be mobbed, with lots of males attempting to mate – this phenomenon is known as a ‘mating ball’. Once mated, the female will head off to excavate a nest tunnel, lining it with a cellophane-like substance that she produces from her salivary glands. This substance is water-proof and contains a fungicide, which helps to protect the pollen and nectar that she gathers from ‘going bad’. This is important because she will lay her eggs on the food that she’s collected, and they won’t hatch until the following summer.
Another hazard for the female ivy bee is that a beetle has evolved a sophisticated method of feeding its own larvae at the expense of the young bees. The ivy bee blister beetle (Stenoria analis) lays its eggs close to the nesting tunnels of the ivy bees. These hatch into larvae known as triongulins because of the three claws on their feet. The newly-hatched male ivy bees approach these larvae, and behave in a very peculiar way, sometimes attempting to mate with them. It’s thought that this might be because the triongulins produce a pheromone that mimics the smell of a female. The small individual larvae also clump together in a way that may resemble the shape of a bee, though looking at them individually this seems rather unlikely. Once the male comes close enough, the triongulins will ‘hop on’ and wait for the next stage of their extraordinary journey.
The male ivy bee, now festooned with beetle larvae, will eventually find a ‘real’ female to mate with, and in the blink of an eye will transfer to her. They will ride back to the female’s nest tunnel, hop off and imbed themselves in the wall, allowing themselves to be sealed in with all that lovely nectar and pollen and, sadly, with the bee egg. The triongulin eats the egg first and then gobbles up all the supplies. If more than one beetle larva ends up in the same nest, one of them will eat the other one too. In the following summer, a new beetle emerges, and the cycle begins all over again.
I am always amazed at the complexity of the relationship between parasites and their hosts. It must be such an ‘arms race’ for each species involved, each one evolving new ways of outwitting the other. According to my Field Guide to the Bees of Great Britain and Ireland, it appears that the ivy bee blister beetle currently only parasitizes ivy bees in the Channel Islands rather than on mainland Britain. It will be interesting to see how long it takes to arrive on the South Coast. I find myself hoping that this attractive little bee will have at least a few years to enjoy the ivy flowers without being harassed.
So, if you have any ivy flowers around, do take a closer look at those ‘honeybees’. In my local area my favourite ivy ‘shrub’, which used to harbour a bumblebee nest, has been cut right back, so no chance of any ivy bees there. Ivy is a remarkable resource for all kinds of pollinators in the late autumn when everything else has died back, and a fine place for birds to nest in the spring. I do realise that it can be a menace when it’s climbing a wall, but I would put in a plea for gardeners to leave it where it isn’t causing a major problem. The ivy bees will love you for it.
Photo One by By Slimguy – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=51455849
Photo Two by By Pjt56 — Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=62016106
Photo Three by By Charles J Sharp – Own work, from Sharp Photography, sharpphotography, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=51348999