Tansy Beetles are small, iridescent green beetles that measure about 1cm long. There are lots of small green beetles in the UK so why is this one so interesting?
Tansy Beetles are almost exclusively endemic to a small stretch of the River Ouse in Yorkshire. In 2014, a few of them were also spotted next to a fen in Cambridgeshire but that’s it, a very small area of the UK! It’s very unusual for a UK animal to only be found in such a small area because the UK is not a very big landmass and it doesn’t have a huge diversity of habitats. Many animals and plants found in Britain can live both in the north of Scotland and the south of England, for example water voles and cabbage white butterflies.
Tansy Beetles are specialists – they mainly eat a plant called ‘tansy’ and their whole life cycle is dependent on the plant.
They eat a couple of other types of plants as well but don’t breed as well on them. They are so specialised that, although they have wings, they rarely fly away from a tansy plant – or go very far away from it at all. However, they much prefer to live on tansy plants which are growing next to a river, making them even more dependent on a small habitat area.
Tansy Beetle adults survive the winter by burrowing into the soil underneath tansy plants. Although the river Ouse floods a lot in the winter, the beetles seem to survive being waterlogged. Summer floods are more dangerous though as the beetle larvae are above ground and are therefore vulnerable to drowning.
If you are walking down the River Ouse in April, May, August or September, see if you can spot the shiny beetles – there are usually loads if you know where to look.