One of the inevitable consequences of climate change is there are now many more species on the move, even without human assistance. Thus in Britain, new species arrive from Europe continually, and gardeners with an interest in wildlife are often among the first to notice.
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Colonisation can be a gradual process. New species of mobile animals, such as moths and bees, arrive here all the time, but it’s only when they establish a permanent breeding population that we decide to call them new residents. But how well do we know what was here in the first place?
For example, another one or two species have been added to our 650-700 species of spider every year since the 1950s. Most of these are assumed to be previously overlooked natives, although a lot of the time no one really knows.
New bee and spider species in UK gardens
Two new bees
In the UK, we had only 26 native species of bumblebees, two of which have been lost from Britain since 1900. Several bumblebees are found in Europe, but not in Britain, and one that always looked like it probably ought to be here is the tree bumblebee, Bombus hypnorum. The tree bumblebee is found throughout much of Europe, it seems to like gardens, and it generally became more abundant during the 20th century. So no one was very surprised when a specimen was captured on the northern edge of the New Forest in 2001.
"The tree bumblebee spread rapidly"
After that first sighting, the tree bumblebee spread rapidly, with the first records from Wales in 2009, from Scotland in 2013 and Ireland in 2014. I saw it for the first time in my old Sheffield garden in 2010,
and by 2015 it was the commonest bumblebee in the neighbourhood.
British bumblebees generally nest in holes in the ground, or on the surface in tussocky grassland, but the tree bumblebee nests in holes in trees and is particularly fond of nest boxes provided for birds. Your
local blue tits might be annoyed by that, but I wouldn’t worry – like all bumblebees, Bombus hypnorum is a useful pollinator and completely harmless as long as you leave them alone.
You almost certainly have tree bumblebees in your garden, and fortunately they look nothing like our native bees, with a ginger thorax, black abdomen and white tail – a bit like a furry mint humbug.
"Most of our bees are solitary, often quite small and not always easy to identify"
Unlike honeybees and bumblebees, most of our bees are solitary, often quite small and not always easy to identify. But there’s one solitary bee that you can’t have missed if you’ve been on holiday to southern Europe, and which also illustrates the difficulty of knowing when a species has become a genuine UK resident. Xylocopa violacea, the violet carpenter bee, is a large black, shiny bee, about the size of a large queen bumblebee, with iridescent violet-blue wings.
The violet carpenter bee has been spreading northward in Europe, and occasional interlopers have often crossed the Channel. Carpenter bees nest in wood such as dead trees, felled timber and fence posts, so it may also arrive in imported timber. The female bee uses its powerful mandibles to excavate a tunnel, then lays eggs in cells, which are stocked with nectar and pollen. Like other solitary bees, when nesting is finished the female leaves the larvae to develop on their own. Adult bees may hibernate in hollow trees or similar sites.
"Young spiderlings can travel hundreds of kilometres by ballooning"
For nearly 20 years now, there have been sporadic reports of carpenter bees overwintering or even breeding in Britain, and there seems no doubt it’s on its way to becoming a resident species, if it isn’t already. It’s worth keeping a look out for it – there’s nothing else like it in Britain.
A new spider
Something else worth looking out for is the wasp spider (Argiope bruennichi). Many spiders are a nightmare to identify, but this one is big and completely unmistakable, and also builds an unusual orb web, with a zigzag band of silk down the middle. This European spider was first recorded in East Sussex in 1922 and has been slowly extending its range ever since.
The wasp spider has been moving north and west in Europe for at least a century, almost certainly in response to a warming climate, and young spiderlings can travel hundreds of kilometres by ballooning (travelling on the wind on sail-like webs they have spun), so it could easily have got here on its own. If it did, that means it’s now technically a new British native. On the other hand, there are claims of
at least one human introduction, and it seems to have spread from at least three centres of introduction, so maybe it arrived by both means? Either way, it’s obviously here to stay.
Room for one more?
Of all the species lurking just across the Channel, which one do I wish would successfully establish here? Well, my favourite would have to be the European tree frog. It has established a few short-lived populations in the wild (probably escaped pets), and a few optimists suggest it’s actually a long-lost British native. It’s also dead cute. Definitely one to watch for the future.
Here's more on making your garden wildlife friendly