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We are nudging towards the end of October with days of cold rain getting more frequent. There was snow on the distant hills across the Firth yesterday and skeins of geese moving across the sky. However, on warm sunny days I still see Himalayan balsam pollen coming into the home apiary hives after three months. Viburnum is flowering in the garden, and ivy is blooming, still.
Recently I met Graham from Nairn who has been smitten with bee fever. He wants to know about all our bees and get his hands on good books to help him identify insects and learn about their behaviour. This blog is for you Graham and you can spend the remaining sunny days of autumn scanning the ivy to see if the ivy bee has arrived up here yet. It is not long ago we saw our first sighting of the tree bumble bee in Nairnshire.
We hear so much about the decline in pollinators and the extinction of some bumble bee species but this is a good new story. In 2001 a plasterer bee called the ivy bee, or Colletes hederae, was first spotted in Dorset. It moved up the coast arriving in Pembrokeshire Wales in 2014. It reached other places in Britain before flying across from Wales in 2021 to the east coast of Ireland 60 miles away in Wexford.
The ivy bee came over from Central Europe but is a new kid on the block having been known to science only since 1993. It may have been around for a lot longer and might have been confused with another plasterer bee called Colletes haliophilus, or sea aster. However, the ivy bee is now officially classed and documented as a subspecies in the family Colletidae.
The ivy bee is about the same size as a honey bee but has distinctive stripes and a reddish/brown thorax. The female has the more colourful orangey thorax. Like all bees, females have a sting, but, unlike the honey bee sting, the ivy bee sting is little more than a mild irritation rather like a stinging nettle. This is according to Professor Francis Ratnieks who is experienced in such matters.
When Tony Harris and I organised the Scottish Beekeeping Convention in 2016, Tony led a visit to his bees on the heather moors on Ben Rinnes. It was the end of the season and a bit brisk up on the hill with a chilly breeze. The nectar flow was over and the bees were naturally defensive though not nasty. All of a sudden Professor Ratnieks went sprinting down the hill past us at a competitive pace with Professor Seeley not far behind. Both our esteemed speakers had declined our advice about getting well suited up for the visit and they paid the price. They had a terrific time at our convention though and the next stop was a whisky distillery tour. Professor Ratnieks said it was the best fun he had ever had at a convention.
Dr Francis Ratnieks is Professor of Apiculture at Sussex University and one of our most respected scientists here in the UK. He and his team are doing a lot of work on forage and nutrition which is helpful to us beekeepers. Francis tells a wonderful story of the fascinating ivy bee in a two-part interview on Irish radio RTE https://www.rte.ie/radio/radio1/clips/22242332/. I really enjoyed listening to these broadcasts which are delivered slowly and clearly and I think that you will enjoy them too.https://www.rte.ie/radio/radio1/clips/22304068/
Ivy Bee Life Cycle.
The life cycle is so interesting because it takes a year from egg to emergence as a mature adult which is unlike many other bee life histories. As the name implies, this bee feeds on ivy which is prolific in many parts of the UK and Ireland (ROI), and blooms for around 3 months at the end of summer and well into autumn. For people worried that the ivy bee might displace other insects in competition for forage, fear not. Professor Ratnieks has been studying this too and reassures us that despite ivy being so popular with many insects, about half the pollen and nectar is wasted. During its three-month bloom, ivy provides 75-90% nectar and pollen to all insects and they don’t need long tongues to access the nectaries.
This British climbing plant, sometimes known as common, Atlantic, or English ivy, thrives clinging to tree trunks in woodlands where the soil is not acidic. It clutches old walls and rocks and acts as ground cover, creeping over land as an immature plant searching for something to climb. Ivy has its own root system so cannot be accused of parasitism.
Hedera helix is one of two ivy species found in the UK. The other is Irish ivy, Hedera hibernica, which is so similar that they can only be told apart by the hairs below the flowers which are white in H. helix, and yellow-green or yellow-brown in colour in H. hibernica.
The small greenish yellow flowers are malodourous attracting carrion flies. However, many other pollinators are attracted to its high levels of concentrated nectar making ivy an important autumn flowering plant. Flowering times vary across the country but where I live in the Scottish Highlands it usually flowers from early October till November.
The nectaries are situated in the pistil with nectar being secreted by a yellow-green disc surrounding the styles. Nectar flows copiously and I’ve seen crusty sugary crystals covered by bees, small flies, butterflies, hover flies, ants and wasps. Not only does ivy provide late forage for honey bees, but it gives the solitary ivy bee-Colletes Hederae-all its pollen and nectar requirements. The latter, a newcomer to the UK, was found in 2001 in Dorset, and it is heading north having been spotted in Shropshire and Wales. Because the nectar is so concentrated it requires less work for honey bees to evaporate excess water so is an ideal late crop for winter storage. Ivy honey is greenish in colour with an aromatic flavour and granulates quickly due to high glucose content.
Ivy pollen is a dull yellow colour with medium sized individual grains of between 35-50µm. Like many pollen grains, ivy has 3 apertures on the exine which allow the grains to dry out or to absorb water. However, the key function is providing an exit for the germinating pollen tube carrying the reproductive cells from the pollen grain to the ovule. These apertures are covered by a thin membrane designed to rupture under pressure when the pollen tube bursts through.
The leaves of immature non-flowering ivy are dark green matt and heart shaped with five lobes. They creep along the ground searching for something to climb where they will mature and flower. The leaves then become a lighter shiny green and more oval shaped with a pointed end. Leaf size varies—see drawing of correctly scaled leaves.
Beekeepers need to be aware that if Asian hornets-Vespa Velutina- make an incursion into their area they are likely to be found on ivy craving sugar at end of summer so monitoring local ivy should be part of our regular surveillance routine.
Ivy Bee Life Cycle.
In September the first new ivy bees of the year emerge as adults from their underground nests. They are soon on the wing and mating after which they start digging tunnels to nesting places where they build cells and provision them with nectar and pollen. With their mandibles, they fashion transparent cellophane-like lining for the tunnels to keep the larvae safe over the long period till the following autumn. The females have a gland called the Dufour gland near the sting that secretes the material needed to make this protective lining. These bees are solitary in that there is only one generation of bee in the nest and they do not cooperate with each other as in social bee colonies. Each queen produces around 10-20 cells and fills each with an egg. She seals up the nest and leaves the offspring with all the food they need till emergence. The mother’s job is done and she dies. There are many tunnels and nests in one area and up to thousands in what is termed nest aggregation. This “housing estate “strategy provides collective safety as they may be less at risk from predators, but the nests are the work of individual females.
Professor Ratnieks describes a mating ball where a couple engaged in mating are in the middle and 5 to 20 males are surrounding them hoping for a bit of action themselves. There is only one predator of the ivy bee and it is a parasitic type of European beetle fortunately not found over here.
The ivy bee population is over 25,000 in UK and thriving. In September 2021 the first recorded sighting in Scotland was on the East coast at Dunbar. You can use this app App iRecord if you spot what looks like an ivy bee, and BWARS will be interested to hear from you too. This is the team that confirms sightings and keeps records of bees, wasps, and ants in UK.
For more information and photos of ivy bees, visit Philip’s lovely nature blog here https://philipstrange.wordpress.com/2023/10/16/ivy-bees-and-a-dipper-by-the-river-ashburn/#like-4883