I had not seen one of these beautiful insects before last Thursday. They are relatively recently discovered, only being described as a species in 1993, and making their first appearance in Britain in 2001, when they were discovered in Dorset. Since then their spread across the United Kingdom has been steady. The Ivy Bee is one of a number of ground nesting solitary bees in Britain but unlike others they are very late flying, typically emerging at the beginning of September when most other species are dwindling. That said, my sighting last week was particularly late, perhaps due to the mild weather we have been experiencing.
In terms of identification they are difficult to confuse for other species because of this late flying period but they do have a few diagnostic features too. For example, the banding on the abdomen is quite bright and almost wasp-like though a little more orange in colour, and they have a rather wonderful furry thorax which is a lovely ginger colour. As the name suggests, they feed exclusively on Ivy. Males and females can be distinguished by size with the males being much smaller than the females. Like many other ground nesting solitary bees, they dig burrows in loosely packed, usually sandy, soil with each pair having their own hole up to a foot or more deep. In this, they tend up to 18 brood chambers which are each lined and provisioned with pollen for the growing young. Their life span as an adult is only about 3-6 weeks but they will spend around 10 months as a larva in the brood chamber.
Unlike most other bees there are no specific parasites which target Ivy bees. This is unusual but can be said to prove that they are a recently evolved species, as more established species tend to have associated predators and parasites that have evolved with them. There are a few generalists such as spiders and birds which may take a few individuals, but there are few other threats to the Ivy bee and this may well play a part in the speed of their spread. The Ivy bee doesn’t tend to fly in temperatures below about 14 degrees centigrade and so global warming may be a contributing factor to their rapid distribution too. The speed with which they have colonised the UK to date has been astonishingly fast with latest records showing they have reached North Wales. The nice thing about the Ivy bee though, is that while an invasion like this in other species might be a little concerning, there is no evidence that they are anything but good – they don’t harm anything or fill any niche that might out compete other native species – they are a welcome addition to our British wildlife.
The Bees Wasps and Ants Recording Society are mapping their progress across the country and there are very few records on the map, so being able to contribute to the data they are collecting is quite exciting, particularly as I don’t tend to do much in the way of biological recording and really think I ought to do more – what better way to kick start my recording!?
This encounter got me thinking too though. The weather has been unseasonably warm so far this month and along with the glorious little Ivy Bee were a whole host of other invertebrates making the most of the late nectar source. Two species of butterfly (Red Admiral and Comma) were drinking in the sun as well as the nectar, while at least 3 species of hoverfly joined wasps and honey bees and even a lone bumblebee on the little green blooms. I found myself wondering how much scent plays a part in advertising the blossom to potential pollinators, as it was really quite strong and I knew it was flowering long before I reached the plant. One of the reasons it is so important as a source of nectar is that Ivy has a long flowering season of 2-3 months from September into November, with each umbel of flowers lasting longer by flowering from the outside inwards and providing a constant source of nectar.
It isn’t just the flowers that are vital for wildlife though, later on the berries become another food source for many hedgerow birds such as woodpigeon and thrushes including some of our winter visitors like Redwing and Fieldfare. The berries are less conspicuous than many being bluish-black in colour. Nevertheless they are highly nutritious, with the pith being particularly calorific, and by eating the berries the birds do the plant a favour too as the seeds will pass through unharmed and be spread elsewhere with a generous helping of fertiliser to boot. Indeed, as many as 70 species of insect have been recorded nectaring on the flowers and up to 16 species of bird use the berries as a food source, while deer are known to browse on the leaves in winter. The ivy plant becomes a vital source of shelter in winter too, both for a huge variety of insects including favourites like ladybirds and for birds, particularly if it is a thick covering as the overlapping leaves provide a barrier against the weather and help to trap warmer air pockets.
Many people believe that Ivy will strangle and kill a tree once it gets a grip. There is much debate over this, though the general consensus is that this is not the case. There is naturally competition between the tree and the ivy for nutrients, water and light, the latter of which may well be the reason that the ivy climbs the tree in the first place. In smaller trees the ivy can become so prolific as to topple them over, but there is little evidence to say that the Ivy will kill a healthy tree otherwise. And so to the gardeners out there, if you want to improve your garden for wildlife, Ivy must be a serious consideration. It is an attractive climbing plant which will cope with little intervention but it is also invaluable to a great number of species, the Ivy Bee included.