TANSY BEETLE

Chysolina Graminis

Chrysolina graminis.jpg

A spectacular, large, green leaf beetle, with a distinctive coppery sheen. The Tansy beetle is one of our most stunning insects.

  • Rarity: The Tansy beetle is restricted to a 45km stretch of riverbank centred on York, as well as two small areas in the Cambridgeshire/Norfolk Fens
     

  • Causes of decline: The Tansy beetle is dependent on Tansy plants along the River Ouse, which are becoming more scattered due to changes of land use and competition with invasive plants; and declines are also caused by summer flooding

The Tansy beetle is an iridescent green leaf beetle that is affectionately known as the Jewel of York. This beautiful beetle is roughly 1cm long - about a quarter of the size of a one pence coin. The Tansy beetle was once more widespread in Britain, but this striking beetle is now restricted to the banks of the River Ouse (near York) and small areas of the Cambridgeshire Fens. The declines in the Tansy beetle's population and restricted location means it is a conservation priority and so is listed as Endangered (at risk of extinction) on the national Red List of threatened species.

The banks of the River Ouse near York are a nationally important area for the Tansy beetle, where a large proportion of the British population is found. Therefore, it is important that the banks are in part managed for the Tansy beetle and its York food-plant, Tansy. Tansy Tanacetum vulgare, with its yellow button-like flowers, is a common plant that is often see growing on riverbanks in clumps. 

​Threats to the Tansy beetle on the Ouse, include:

  • Tansy plants uprooted when mistaken for Ragwort Senecio jacobaea

  • Tansy plant and Tansy beetles eaten by high numbers of grazing animals

  • Tansy clumps over-shadowed by willow or out-competed by the invasive plant Himalayan balsam Impatiens glandulifera

  • Mowing the riverbank when the beetle is vulnerable (March to October)

  • Bank erosion and summer flooding

When planning riverbank management it is important to consider any work in conjunction with the beetle’s life cycle. The Tansy beetle is particularly vulnerable during the reproductive phase of its life cycle i.e. between March and September. Cutting and other operations that remove Tansy plants should be avoid during this time.